<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2022 Workiva-->
<!--r:ee2ea18c-1ca1-46a1-a6f7-74b117204738,g:3fde056d-4910-48b2-92f4-0dd99a5fa758-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.bentley.com/role/Cover" xlink:type="simple" xlink:href="bsy-20220331.xsd#Cover"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/Cover" xlink:type="extended" id="i52e25c06f8794a7fa65b56e92d3a8e01_Cover">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_dae625ce-47bb-4c59-bac4-48dfa894bbe3" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_DocumentType_dae625ce-47bb-4c59-bac4-48dfa894bbe3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_96dbcf2a-d39d-49ca-a4b6-d2de016309c9" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_DocumentQuarterlyReport_96dbcf2a-d39d-49ca-a4b6-d2de016309c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_74d88db1-d486-4a59-90be-8dc0303c36bb" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_DocumentPeriodEndDate_74d88db1-d486-4a59-90be-8dc0303c36bb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_a474a480-edaf-473d-a771-cc7ce3e795f9" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_DocumentTransitionReport_a474a480-edaf-473d-a771-cc7ce3e795f9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_0c54a4e2-de62-4922-94c0-504d66e9ee0b" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_EntityFileNumber_0c54a4e2-de62-4922-94c0-504d66e9ee0b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_fb092ce5-21a3-48a5-a74c-9dcff13c71f7" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_EntityRegistrantName_fb092ce5-21a3-48a5-a74c-9dcff13c71f7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_d6019ea4-9e88-454b-a3db-f71b56fa1a1a" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_EntityIncorporationStateCountryCode_d6019ea4-9e88-454b-a3db-f71b56fa1a1a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_ae89b99b-2f2b-4059-848c-b0c56394c159" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_EntityTaxIdentificationNumber_ae89b99b-2f2b-4059-848c-b0c56394c159" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_613b7709-93c8-4bc1-b179-a5b279f7a3f4" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_EntityAddressAddressLine1_613b7709-93c8-4bc1-b179-a5b279f7a3f4" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_b6e007a0-dfc7-4d79-986e-0854b6d0e3d2" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_EntityAddressCityOrTown_b6e007a0-dfc7-4d79-986e-0854b6d0e3d2" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_cfc321e2-1a8a-425e-83f8-59ca47ec19dd" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_EntityAddressStateOrProvince_cfc321e2-1a8a-425e-83f8-59ca47ec19dd" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_1ff52bba-c865-4fed-a594-09f62c4fd7ba" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_EntityAddressPostalZipCode_1ff52bba-c865-4fed-a594-09f62c4fd7ba" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_43e5a009-8b1d-4520-b51a-2547dd78b121" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_CityAreaCode_43e5a009-8b1d-4520-b51a-2547dd78b121" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_918b134a-541b-4964-ba11-e1d1b24d491d" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_LocalPhoneNumber_918b134a-541b-4964-ba11-e1d1b24d491d" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_55a2158d-9bf4-4dc5-af3d-532daf618617" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_Security12bTitle_55a2158d-9bf4-4dc5-af3d-532daf618617" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_e9609221-df4b-4a82-9182-986906ad2b7f" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_TradingSymbol_e9609221-df4b-4a82-9182-986906ad2b7f" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_7b90de38-f2db-47c9-882c-a8cf24648cc2" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_SecurityExchangeName_7b90de38-f2db-47c9-882c-a8cf24648cc2" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_06fb301d-ff78-4b2b-a994-97dd7a9688fd" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_EntityCurrentReportingStatus_06fb301d-ff78-4b2b-a994-97dd7a9688fd" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_1f4dedf8-ec0e-4fd4-97b5-0f4e0ec396be" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_EntityInteractiveDataCurrent_1f4dedf8-ec0e-4fd4-97b5-0f4e0ec396be" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_ea3852e9-8494-4143-a63e-4fca51762a9f" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_EntityFilerCategory_ea3852e9-8494-4143-a63e-4fca51762a9f" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_823b760e-7406-4ba5-a9ce-0a1a35f96e2e" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_EntitySmallBusiness_823b760e-7406-4ba5-a9ce-0a1a35f96e2e" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_8ead2501-4ab1-46c6-8aac-e17009be17d5" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_EntityEmergingGrowthCompany_8ead2501-4ab1-46c6-8aac-e17009be17d5" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_e5c629ea-47d0-4423-93ae-db13026a6da4" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_EntityShellCompany_e5c629ea-47d0-4423-93ae-db13026a6da4" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_6e885783-af01-4ac3-b18a-48dffdbe925c" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_6e885783-af01-4ac3-b18a-48dffdbe925c" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_e24d0fb6-0d52-405e-8575-e3d05625c401" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_CurrentFiscalYearEndDate_e24d0fb6-0d52-405e-8575-e3d05625c401" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_e75f4048-70bb-407a-9eb8-07d97bf6b431" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_EntityCentralIndexKey_e75f4048-70bb-407a-9eb8-07d97bf6b431" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_0e932095-c498-4448-8f5c-5b54fa50b115" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_AmendmentFlag_0e932095-c498-4448-8f5c-5b54fa50b115" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_2be19f59-2883-47a1-a8af-0e45350aec31" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_DocumentFiscalPeriodFocus_2be19f59-2883-47a1-a8af-0e45350aec31" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_be3b4d7d-3c9e-4838-b2bb-4edcbd073523" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_DocumentFiscalYearFocus_be3b4d7d-3c9e-4838-b2bb-4edcbd073523" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_10f539a1-a269-4bc0-8e46-42b94acd5c76" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_9f3d8f04-18a4-4d88-8078-2d62574ba967" xlink:to="loc_dei_DocumentInformationTable_10f539a1-a269-4bc0-8e46-42b94acd5c76" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_f1571d6d-23a4-4895-9583-8449344c45e7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_10f539a1-a269-4bc0-8e46-42b94acd5c76" xlink:to="loc_us-gaap_StatementClassOfStockAxis_f1571d6d-23a4-4895-9583-8449344c45e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_f1571d6d-23a4-4895-9583-8449344c45e7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_f1571d6d-23a4-4895-9583-8449344c45e7" xlink:to="loc_us-gaap_ClassOfStockDomain_f1571d6d-23a4-4895-9583-8449344c45e7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_022c8b36-eea6-4376-ae72-ee305b26c5d4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_f1571d6d-23a4-4895-9583-8449344c45e7" xlink:to="loc_us-gaap_ClassOfStockDomain_022c8b36-eea6-4376-ae72-ee305b26c5d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_74c1e769-4c09-49a1-9984-ee0f09e31d89" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_022c8b36-eea6-4376-ae72-ee305b26c5d4" xlink:to="loc_us-gaap_CommonClassAMember_74c1e769-4c09-49a1-9984-ee0f09e31d89" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_61f7fb1e-6cb4-4c92-a46a-f3cbad7bd73f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_022c8b36-eea6-4376-ae72-ee305b26c5d4" xlink:to="loc_us-gaap_CommonClassBMember_61f7fb1e-6cb4-4c92-a46a-f3cbad7bd73f" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="simple" xlink:href="bsy-20220331.xsd#ConsolidatedBalanceSheetsParenthetical"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="extended" id="if4bac1d6930e4b899cd0f9dac868496b_ConsolidatedBalanceSheetsParenthetical">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_6e1d6b20-2b0b-4b69-a417-c3d48ad8aa8b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_488f3e91-5f3a-4099-b3c8-3aae385eaa66" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PreferredStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6e1d6b20-2b0b-4b69-a417-c3d48ad8aa8b" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_488f3e91-5f3a-4099-b3c8-3aae385eaa66" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_d916feca-a90a-47ff-9371-e6c287a7b1e3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6e1d6b20-2b0b-4b69-a417-c3d48ad8aa8b" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_d916feca-a90a-47ff-9371-e6c287a7b1e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued_b4614c1c-f2ba-444d-ac5d-fa5d72a93ae8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6e1d6b20-2b0b-4b69-a417-c3d48ad8aa8b" xlink:to="loc_us-gaap_PreferredStockSharesIssued_b4614c1c-f2ba-444d-ac5d-fa5d72a93ae8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_ff7df304-a39e-486d-acb2-543822323269" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6e1d6b20-2b0b-4b69-a417-c3d48ad8aa8b" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_ff7df304-a39e-486d-acb2-543822323269" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_ae58076f-b09c-4793-8136-67a875a06a67" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6e1d6b20-2b0b-4b69-a417-c3d48ad8aa8b" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_ae58076f-b09c-4793-8136-67a875a06a67" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_9c591cd0-241c-44d4-89a0-60dfcd88654b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6e1d6b20-2b0b-4b69-a417-c3d48ad8aa8b" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_9c591cd0-241c-44d4-89a0-60dfcd88654b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_07a2c480-636d-4cf4-b840-85f1e8010ffc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6e1d6b20-2b0b-4b69-a417-c3d48ad8aa8b" xlink:to="loc_us-gaap_CommonStockSharesIssued_07a2c480-636d-4cf4-b840-85f1e8010ffc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_26d7d8b6-8c0b-4b0b-8e9e-614c5ec36957" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6e1d6b20-2b0b-4b69-a417-c3d48ad8aa8b" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_26d7d8b6-8c0b-4b0b-8e9e-614c5ec36957" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_5f4d5294-6b83-438a-ab34-83b6cc25db11" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_6e1d6b20-2b0b-4b69-a417-c3d48ad8aa8b" xlink:to="loc_us-gaap_StatementTable_5f4d5294-6b83-438a-ab34-83b6cc25db11" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_faf6c5cb-bb73-4120-933c-5bf8cd42a42d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_5f4d5294-6b83-438a-ab34-83b6cc25db11" xlink:to="loc_us-gaap_StatementClassOfStockAxis_faf6c5cb-bb73-4120-933c-5bf8cd42a42d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_faf6c5cb-bb73-4120-933c-5bf8cd42a42d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_faf6c5cb-bb73-4120-933c-5bf8cd42a42d" xlink:to="loc_us-gaap_ClassOfStockDomain_faf6c5cb-bb73-4120-933c-5bf8cd42a42d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_f08f4608-2046-4264-8e09-c8830d2421a2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_faf6c5cb-bb73-4120-933c-5bf8cd42a42d" xlink:to="loc_us-gaap_ClassOfStockDomain_f08f4608-2046-4264-8e09-c8830d2421a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_5ae09257-b271-4100-b977-40cae4312cca" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_f08f4608-2046-4264-8e09-c8830d2421a2" xlink:to="loc_us-gaap_CommonClassAMember_5ae09257-b271-4100-b977-40cae4312cca" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_30a45c72-7a94-40e9-987f-aa9f4cd490ba" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_f08f4608-2046-4264-8e09-c8830d2421a2" xlink:to="loc_us-gaap_CommonClassBMember_30a45c72-7a94-40e9-987f-aa9f4cd490ba" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/ConsolidatedStatementsofOperations" xlink:type="simple" xlink:href="bsy-20220331.xsd#ConsolidatedStatementsofOperations"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/ConsolidatedStatementsofOperations" xlink:type="extended" id="ie8dd50d344914a9987741f2b8d494e0a_ConsolidatedStatementsofOperations">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_41a7174f-bdff-41bb-a7ea-39ba60c5e5be" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_ce850940-73c2-44d6-9367-9c875b7f3ae8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_41a7174f-bdff-41bb-a7ea-39ba60c5e5be" xlink:to="loc_us-gaap_RevenuesAbstract_ce850940-73c2-44d6-9367-9c875b7f3ae8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_088d32e5-ac60-4503-ba08-14597b52e81f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_ce850940-73c2-44d6-9367-9c875b7f3ae8" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_088d32e5-ac60-4503-ba08-14597b52e81f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenueAbstract_6a3df9ad-67ca-497d-b1f5-7d6f449bf7a9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CostOfRevenueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_41a7174f-bdff-41bb-a7ea-39ba60c5e5be" xlink:to="loc_us-gaap_CostOfRevenueAbstract_6a3df9ad-67ca-497d-b1f5-7d6f449bf7a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenue_74f17b63-dacc-44cf-898d-20bc947a3596" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CostOfRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostOfRevenueAbstract_6a3df9ad-67ca-497d-b1f5-7d6f449bf7a9" xlink:to="loc_us-gaap_CostOfRevenue_74f17b63-dacc-44cf-898d-20bc947a3596" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_4ff38b98-a78b-4ed8-b2ec-bb9631922f4f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_41a7174f-bdff-41bb-a7ea-39ba60c5e5be" xlink:to="loc_us-gaap_GrossProfit_4ff38b98-a78b-4ed8-b2ec-bb9631922f4f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_b1d72f6f-12e9-4420-9053-499eed17d1cf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_41a7174f-bdff-41bb-a7ea-39ba60c5e5be" xlink:to="loc_us-gaap_OperatingExpensesAbstract_b1d72f6f-12e9-4420-9053-499eed17d1cf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_e5bc1802-0122-4df9-9181-af47cfa8aaad" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_b1d72f6f-12e9-4420-9053-499eed17d1cf" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_e5bc1802-0122-4df9-9181-af47cfa8aaad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpense_05500b98-d02c-4f68-a5a9-cffaa2253fad" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SellingAndMarketingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_b1d72f6f-12e9-4420-9053-499eed17d1cf" xlink:to="loc_us-gaap_SellingAndMarketingExpense_05500b98-d02c-4f68-a5a9-cffaa2253fad" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_6c83e1e2-ae2d-428e-9290-32172cb27ce8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_b1d72f6f-12e9-4420-9053-499eed17d1cf" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_6c83e1e2-ae2d-428e-9290-32172cb27ce8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense_62c30236-8186-4670-9e0b-d2b1bcc6067d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_b1d72f6f-12e9-4420-9053-499eed17d1cf" xlink:to="loc_us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense_62c30236-8186-4670-9e0b-d2b1bcc6067d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_80e7a632-aa1b-4c77-b815-b2068723f5e3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_b1d72f6f-12e9-4420-9053-499eed17d1cf" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_80e7a632-aa1b-4c77-b815-b2068723f5e3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_96f78196-7447-4398-b4f1-072e9adb2beb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_b1d72f6f-12e9-4420-9053-499eed17d1cf" xlink:to="loc_us-gaap_OperatingExpenses_96f78196-7447-4398-b4f1-072e9adb2beb" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_4dd76271-fe3f-490b-8e0e-5b59ed5283e2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_41a7174f-bdff-41bb-a7ea-39ba60c5e5be" xlink:to="loc_us-gaap_OperatingIncomeLoss_4dd76271-fe3f-490b-8e0e-5b59ed5283e2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_2040c522-48dd-4721-bd68-22a77af7e9f6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestIncomeExpenseNonoperatingNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_41a7174f-bdff-41bb-a7ea-39ba60c5e5be" xlink:to="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_2040c522-48dd-4721-bd68-22a77af7e9f6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_e972f6e6-42dc-4290-8d11-660c8c902ba7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_41a7174f-bdff-41bb-a7ea-39ba60c5e5be" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_e972f6e6-42dc-4290-8d11-660c8c902ba7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_86109306-7925-4f7a-a5c2-14846994722a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_41a7174f-bdff-41bb-a7ea-39ba60c5e5be" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_86109306-7925-4f7a-a5c2-14846994722a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_cfdf9a4b-b589-44d2-92ed-5bef3e3fa471" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_41a7174f-bdff-41bb-a7ea-39ba60c5e5be" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_cfdf9a4b-b589-44d2-92ed-5bef3e3fa471" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_0aef87d8-ccd4-4cc2-8e49-aeb97b1420ed" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_41a7174f-bdff-41bb-a7ea-39ba60c5e5be" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_0aef87d8-ccd4-4cc2-8e49-aeb97b1420ed" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_61fbac1d-9c1a-4540-9b2a-0fbff9e5daf2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_41a7174f-bdff-41bb-a7ea-39ba60c5e5be" xlink:to="loc_us-gaap_NetIncomeLoss_61fbac1d-9c1a-4540-9b2a-0fbff9e5daf2" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic_7342af23-faac-4e53-bb75-6bcc6e608d01" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_41a7174f-bdff-41bb-a7ea-39ba60c5e5be" xlink:to="loc_us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic_7342af23-faac-4e53-bb75-6bcc6e608d01" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_e7c302a7-97c0-4c01-a77d-e93436074573" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_41a7174f-bdff-41bb-a7ea-39ba60c5e5be" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_e7c302a7-97c0-4c01-a77d-e93436074573" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_07eaf881-4f8e-4c10-abef-0b3dd65472d3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_41a7174f-bdff-41bb-a7ea-39ba60c5e5be" xlink:to="loc_us-gaap_EarningsPerShareAbstract_07eaf881-4f8e-4c10-abef-0b3dd65472d3" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_bcfee169-1935-4c8b-978c-9f06e2a91404" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_07eaf881-4f8e-4c10-abef-0b3dd65472d3" xlink:to="loc_us-gaap_EarningsPerShareBasic_bcfee169-1935-4c8b-978c-9f06e2a91404" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_537d4728-a939-460b-b138-1410979d0231" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_07eaf881-4f8e-4c10-abef-0b3dd65472d3" xlink:to="loc_us-gaap_EarningsPerShareDiluted_537d4728-a939-460b-b138-1410979d0231" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_bd23e087-e1ff-40bd-8b35-28a5fce19685" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_07eaf881-4f8e-4c10-abef-0b3dd65472d3" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_bd23e087-e1ff-40bd-8b35-28a5fce19685" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_ec0432d0-8420-43f5-ba72-cbe7c256bf09" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_07eaf881-4f8e-4c10-abef-0b3dd65472d3" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_ec0432d0-8420-43f5-ba72-cbe7c256bf09" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_aa1caaa2-98de-4786-bbfe-028842156146" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_41a7174f-bdff-41bb-a7ea-39ba60c5e5be" xlink:to="loc_us-gaap_StatementTable_aa1caaa2-98de-4786-bbfe-028842156146" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_5fa90ca0-c484-4ef8-a3ed-4607c1bd8a49" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_aa1caaa2-98de-4786-bbfe-028842156146" xlink:to="loc_srt_ProductOrServiceAxis_5fa90ca0-c484-4ef8-a3ed-4607c1bd8a49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_5fa90ca0-c484-4ef8-a3ed-4607c1bd8a49_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_5fa90ca0-c484-4ef8-a3ed-4607c1bd8a49" xlink:to="loc_srt_ProductsAndServicesDomain_5fa90ca0-c484-4ef8-a3ed-4607c1bd8a49_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_e252761f-7f79-46b4-abf7-b99723d17503" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_5fa90ca0-c484-4ef8-a3ed-4607c1bd8a49" xlink:to="loc_srt_ProductsAndServicesDomain_e252761f-7f79-46b4-abf7-b99723d17503" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_SubscriptionsAndLicensesMember_5b0a7222-24bb-404f-a47b-4367ec73d036" xlink:href="bsy-20220331.xsd#bsy_SubscriptionsAndLicensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_e252761f-7f79-46b4-abf7-b99723d17503" xlink:to="loc_bsy_SubscriptionsAndLicensesMember_5b0a7222-24bb-404f-a47b-4367ec73d036" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubscriptionAndCirculationMember_be2f10a3-4b01-4081-ad9f-8899c1cbc15c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubscriptionAndCirculationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_SubscriptionsAndLicensesMember_5b0a7222-24bb-404f-a47b-4367ec73d036" xlink:to="loc_us-gaap_SubscriptionAndCirculationMember_be2f10a3-4b01-4081-ad9f-8899c1cbc15c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_PerpetualLicensesMember_82123f40-f6ff-47ab-820f-491b7fe290dc" xlink:href="bsy-20220331.xsd#bsy_PerpetualLicensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_SubscriptionsAndLicensesMember_5b0a7222-24bb-404f-a47b-4367ec73d036" xlink:to="loc_bsy_PerpetualLicensesMember_82123f40-f6ff-47ab-820f-491b7fe290dc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceMember_4fbe41bb-c436-45d2-8b86-0a6871d321de" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_e252761f-7f79-46b4-abf7-b99723d17503" xlink:to="loc_us-gaap_ServiceMember_4fbe41bb-c436-45d2-8b86-0a6871d321de" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/ConsolidatedStatementsofStockholdersEquity" xlink:type="simple" xlink:href="bsy-20220331.xsd#ConsolidatedStatementsofStockholdersEquity"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/ConsolidatedStatementsofStockholdersEquity" xlink:type="extended" id="i27ffc5c4634e4685b67003acb76ab5d7_ConsolidatedStatementsofStockholdersEquity">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_c0abfb8b-a731-48b4-9781-4a0acfd6454a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c0abfb8b-a731-48b4-9781-4a0acfd6454a" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_113dde46-1b20-445c-a045-36c0e4eb440e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_113dde46-1b20-445c-a045-36c0e4eb440e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_c81367dc-df06-449f-a607-612c4b095c6f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_us-gaap_StockholdersEquity_c81367dc-df06-449f-a607-612c4b095c6f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_ada314ff-72cf-4038-8058-e7e343c5d458" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_us-gaap_NetIncomeLoss_ada314ff-72cf-4038-8058-e7e343c5d458" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_2918995d-87de-4491-a033-a1a91b62243e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_2918995d-87de-4491-a033-a1a91b62243e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_AdjustmentsToAdditionalPaidInCapitalPurchaseOfCappedCallOptions_a618bb75-49ed-4097-9d19-a416bebff71b" xlink:href="bsy-20220331.xsd#bsy_AdjustmentsToAdditionalPaidInCapitalPurchaseOfCappedCallOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_bsy_AdjustmentsToAdditionalPaidInCapitalPurchaseOfCappedCallOptions_a618bb75-49ed-4097-9d19-a416bebff71b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Dividends_8151771c-1701-4077-b336-4ef9cbb855d2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Dividends"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_us-gaap_Dividends_8151771c-1701-4077-b336-4ef9cbb855d2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_StockIssuedDuringPeriodSharesDeferredCompensationPlan_5d3b7100-6770-4d7d-a6b4-45b14dc8966f" xlink:href="bsy-20220331.xsd#bsy_StockIssuedDuringPeriodSharesDeferredCompensationPlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_bsy_StockIssuedDuringPeriodSharesDeferredCompensationPlan_5d3b7100-6770-4d7d-a6b4-45b14dc8966f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_StockIssuedDuringPeriodValueDeferredCompensationPlan_8606b7de-bdb6-42bd-ae9d-9fc27ea4b0f7" xlink:href="bsy-20220331.xsd#bsy_StockIssuedDuringPeriodValueDeferredCompensationPlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_bsy_StockIssuedDuringPeriodValueDeferredCompensationPlan_8606b7de-bdb6-42bd-ae9d-9fc27ea4b0f7" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_AdjustmentsToAdditionalPaidInCapitalDeferredCompensationPlanVoluntaryContributions_a659f16b-c353-472b-875a-eac8a761b134" xlink:href="bsy-20220331.xsd#bsy_AdjustmentsToAdditionalPaidInCapitalDeferredCompensationPlanVoluntaryContributions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_bsy_AdjustmentsToAdditionalPaidInCapitalDeferredCompensationPlanVoluntaryContributions_a659f16b-c353-472b-875a-eac8a761b134" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesIssuedForServices_48990ba4-ddbf-4ec6-a4c3-c7dfc1db449e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesIssuedForServices"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesIssuedForServices_48990ba4-ddbf-4ec6-a4c3-c7dfc1db449e" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueIssuedForServices_455e74b1-a4de-42c8-96b7-940a771a5792" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueIssuedForServices"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueIssuedForServices_455e74b1-a4de-42c8-96b7-940a771a5792" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_7df76547-5b3e-4818-bdc1-38a356d04fa2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_7df76547-5b3e-4818-bdc1-38a356d04fa2" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_dbabee8a-724b-4587-a2cb-ae884f4bc626" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_dbabee8a-724b-4587-a2cb-ae884f4bc626" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_0a60e879-a066-43fa-8932-c05a6a75c7ba" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_0a60e879-a066-43fa-8932-c05a6a75c7ba" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_848ec29b-fd9a-4135-8f30-b4689eb5d127" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_848ec29b-fd9a-4135-8f30-b4689eb5d127" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_f0327eb5-be70-453c-a48e-045f03147d1c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_f0327eb5-be70-453c-a48e-045f03147d1c" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_fabd482c-6a89-4760-8bc2-b7270900a083" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_fabd482c-6a89-4760-8bc2-b7270900a083" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_3971ccdf-eba7-4a90-8b32-89e2597b5f1a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_3971ccdf-eba7-4a90-8b32-89e2597b5f1a" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_91004581-6848-4baa-ac07-c797f1696b7f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_91004581-6848-4baa-ac07-c797f1696b7f" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_3e8faf34-8f8a-4913-8c63-b7a22eed1903" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2df3dca8-3f2b-4e4e-824b-a2488b4d72e7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_3e8faf34-8f8a-4913-8c63-b7a22eed1903" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_af04ccdf-4853-44a2-876a-4a998c57add8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_1e3df745-3112-403f-bf29-b7d493fa8ec6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_c36f115b-355e-41e4-96c2-217e6af8e8a5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_c0abfb8b-a731-48b4-9781-4a0acfd6454a" xlink:to="loc_us-gaap_StatementTable_c36f115b-355e-41e4-96c2-217e6af8e8a5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_7a744c93-01a1-43db-89b8-9d04c8958437" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_c36f115b-355e-41e4-96c2-217e6af8e8a5" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_7a744c93-01a1-43db-89b8-9d04c8958437" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_7a744c93-01a1-43db-89b8-9d04c8958437_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_7a744c93-01a1-43db-89b8-9d04c8958437" xlink:to="loc_us-gaap_EquityComponentDomain_7a744c93-01a1-43db-89b8-9d04c8958437_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_3c89bcbe-b637-422d-9b09-0d61cc306954" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_7a744c93-01a1-43db-89b8-9d04c8958437" xlink:to="loc_us-gaap_EquityComponentDomain_3c89bcbe-b637-422d-9b09-0d61cc306954" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_24b1fb40-d34a-435c-9e53-7d3a47e3c755" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3c89bcbe-b637-422d-9b09-0d61cc306954" xlink:to="loc_us-gaap_CommonStockMember_24b1fb40-d34a-435c-9e53-7d3a47e3c755" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_b7c59902-aaa3-46f1-96cd-b1919185e578" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3c89bcbe-b637-422d-9b09-0d61cc306954" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_b7c59902-aaa3-46f1-96cd-b1919185e578" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_650c0689-afb3-4205-bcc7-2a4d5f8f4f31" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3c89bcbe-b637-422d-9b09-0d61cc306954" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_650c0689-afb3-4205-bcc7-2a4d5f8f4f31" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_9a957908-d43d-41ce-bcf5-2ddc6714b80e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3c89bcbe-b637-422d-9b09-0d61cc306954" xlink:to="loc_us-gaap_RetainedEarningsMember_9a957908-d43d-41ce-bcf5-2ddc6714b80e" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/BasisofPresentationBusinessCombinationsDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#BasisofPresentationBusinessCombinationsDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/BasisofPresentationBusinessCombinationsDetails" xlink:type="extended" id="iaa6698f93f53404a8610e72971dec977_BasisofPresentationBusinessCombinationsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_e09efcf1-b09e-4d25-8197-84d792e221b0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionContingentConsiderationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_b04139ae-60b3-41ec-94a7-a3791b021c55" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_e09efcf1-b09e-4d25-8197-84d792e221b0" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_b04139ae-60b3-41ec-94a7-a3791b021c55" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_5793bdd6-a755-472e-9701-4a99d429e401" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_e09efcf1-b09e-4d25-8197-84d792e221b0" xlink:to="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_5793bdd6-a755-472e-9701-4a99d429e401" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_7703effa-3059-4290-be8b-d1bf1d23a6dd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_e09efcf1-b09e-4d25-8197-84d792e221b0" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_7703effa-3059-4290-be8b-d1bf1d23a6dd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_eb8d3e1a-4e69-4109-a035-bb3dcaccd48e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_7703effa-3059-4290-be8b-d1bf1d23a6dd" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_eb8d3e1a-4e69-4109-a035-bb3dcaccd48e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_eb8d3e1a-4e69-4109-a035-bb3dcaccd48e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_eb8d3e1a-4e69-4109-a035-bb3dcaccd48e" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_eb8d3e1a-4e69-4109-a035-bb3dcaccd48e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5e7943e8-6e0d-43db-b4f7-591a813df36d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_eb8d3e1a-4e69-4109-a035-bb3dcaccd48e" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5e7943e8-6e0d-43db-b4f7-591a813df36d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_PowerLineSystemsAcquisitionMember_64c5bf0c-4f2d-4a89-8730-239381bb4814" xlink:href="bsy-20220331.xsd#bsy_PowerLineSystemsAcquisitionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5e7943e8-6e0d-43db-b4f7-591a813df36d" xlink:to="loc_bsy_PowerLineSystemsAcquisitionMember_64c5bf0c-4f2d-4a89-8730-239381bb4814" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_SeequentMember_c7790da7-08ec-452c-ace5-240e70ff7fba" xlink:href="bsy-20220331.xsd#bsy_SeequentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5e7943e8-6e0d-43db-b4f7-591a813df36d" xlink:to="loc_bsy_SeequentMember_c7790da7-08ec-452c-ace5-240e70ff7fba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_132c3061-22b8-4f06-840f-1b5f6046e3a3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_7703effa-3059-4290-be8b-d1bf1d23a6dd" xlink:to="loc_us-gaap_StatementClassOfStockAxis_132c3061-22b8-4f06-840f-1b5f6046e3a3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_132c3061-22b8-4f06-840f-1b5f6046e3a3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_132c3061-22b8-4f06-840f-1b5f6046e3a3" xlink:to="loc_us-gaap_ClassOfStockDomain_132c3061-22b8-4f06-840f-1b5f6046e3a3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_7b5befc6-ba5e-4a42-b877-a100062fb4ac" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_132c3061-22b8-4f06-840f-1b5f6046e3a3" xlink:to="loc_us-gaap_ClassOfStockDomain_7b5befc6-ba5e-4a42-b877-a100062fb4ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_f3a20922-8ed4-4eff-be92-c099766a4d08" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_7b5befc6-ba5e-4a42-b877-a100062fb4ac" xlink:to="loc_us-gaap_CommonClassBMember_f3a20922-8ed4-4eff-be92-c099766a4d08" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/RevenuefromContractswithCustomerNarrativeDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#RevenuefromContractswithCustomerNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/RevenuefromContractswithCustomerNarrativeDetails" xlink:type="extended" id="iebbc3abb1c6b4331aa8e629535de5eee_RevenuefromContractswithCustomerNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_8ca5011e-8416-4961-9784-20c7432e44bd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_5dc17e15-4b56-444d-b226-9269840ea792" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_8ca5011e-8416-4961-9784-20c7432e44bd" xlink:to="loc_us-gaap_ContractWithCustomerLiability_5dc17e15-4b56-444d-b226-9269840ea792" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostImpairmentLoss_2fddb412-ad57-41e7-afae-3eef60cd8291" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CapitalizedContractCostImpairmentLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_8ca5011e-8416-4961-9784-20c7432e44bd" xlink:to="loc_us-gaap_CapitalizedContractCostImpairmentLoss_2fddb412-ad57-41e7-afae-3eef60cd8291" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_54bfd470-c634-40c9-b8c7-27a045f264f5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_8ca5011e-8416-4961-9784-20c7432e44bd" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_54bfd470-c634-40c9-b8c7-27a045f264f5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_ContractWithCustomerLiabilityAdditions_a55d947d-505c-483f-9922-4626e43cf259" xlink:href="bsy-20220331.xsd#bsy_ContractWithCustomerLiabilityAdditions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_8ca5011e-8416-4961-9784-20c7432e44bd" xlink:to="loc_bsy_ContractWithCustomerLiabilityAdditions_a55d947d-505c-483f-9922-4626e43cf259" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d394535e-dd03-43dc-b9f8-341f6c6faea3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_8ca5011e-8416-4961-9784-20c7432e44bd" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d394535e-dd03-43dc-b9f8-341f6c6faea3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_4528112f-935a-4a03-8887-07e8ee2b95b8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_8ca5011e-8416-4961-9784-20c7432e44bd" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_4528112f-935a-4a03-8887-07e8ee2b95b8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_fb30e045-b853-49fd-9858-b7ec4af2e252" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_8ca5011e-8416-4961-9784-20c7432e44bd" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_fb30e045-b853-49fd-9858-b7ec4af2e252" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_e7f86606-9b7c-424b-be66-19d0152bde3f" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_fb30e045-b853-49fd-9858-b7ec4af2e252" xlink:to="loc_srt_ProductOrServiceAxis_e7f86606-9b7c-424b-be66-19d0152bde3f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_e7f86606-9b7c-424b-be66-19d0152bde3f_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_e7f86606-9b7c-424b-be66-19d0152bde3f" xlink:to="loc_srt_ProductsAndServicesDomain_e7f86606-9b7c-424b-be66-19d0152bde3f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_d2aae56a-79ff-49d8-babb-e41b784de337" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_e7f86606-9b7c-424b-be66-19d0152bde3f" xlink:to="loc_srt_ProductsAndServicesDomain_d2aae56a-79ff-49d8-babb-e41b784de337" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_PortfolioBalancingExchangeRightsMember_019cad95-8dd8-4208-a32e-3b679e47bb9a" xlink:href="bsy-20220331.xsd#bsy_PortfolioBalancingExchangeRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d2aae56a-79ff-49d8-babb-e41b784de337" xlink:to="loc_bsy_PortfolioBalancingExchangeRightsMember_019cad95-8dd8-4208-a32e-3b679e47bb9a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LicenseMember_5e917315-2d00-48eb-b153-43e55004e870" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LicenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d2aae56a-79ff-49d8-babb-e41b784de337" xlink:to="loc_us-gaap_LicenseMember_5e917315-2d00-48eb-b153-43e55004e870" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TermLicensesMember_79d43827-e46a-47d0-afa4-5055ee81c967" xlink:href="bsy-20220331.xsd#bsy_TermLicensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LicenseMember_5e917315-2d00-48eb-b153-43e55004e870" xlink:to="loc_bsy_TermLicensesMember_79d43827-e46a-47d0-afa4-5055ee81c967" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_55783466-497f-4e8b-af17-ee11ebc0d851" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_fb30e045-b853-49fd-9858-b7ec4af2e252" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_55783466-497f-4e8b-af17-ee11ebc0d851" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_55783466-497f-4e8b-af17-ee11ebc0d851_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_55783466-497f-4e8b-af17-ee11ebc0d851" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_55783466-497f-4e8b-af17-ee11ebc0d851_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_4df142ab-6f78-4d99-b7e1-1b6395153571" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_55783466-497f-4e8b-af17-ee11ebc0d851" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_4df142ab-6f78-4d99-b7e1-1b6395153571" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_503a06d7-b9ee-4464-8b81-71c8c57c1350" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_4df142ab-6f78-4d99-b7e1-1b6395153571" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_503a06d7-b9ee-4464-8b81-71c8c57c1350" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0402ffee-3a40-4d8a-9272-3d0e6fc8b8f3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_fb30e045-b853-49fd-9858-b7ec4af2e252" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0402ffee-3a40-4d8a-9272-3d0e6fc8b8f3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_0402ffee-3a40-4d8a-9272-3d0e6fc8b8f3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0402ffee-3a40-4d8a-9272-3d0e6fc8b8f3" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_0402ffee-3a40-4d8a-9272-3d0e6fc8b8f3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_89e64fef-7d44-4c4f-8f52-7b82c49c540a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0402ffee-3a40-4d8a-9272-3d0e6fc8b8f3" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_89e64fef-7d44-4c4f-8f52-7b82c49c540a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_5ac7fe2d-08db-43eb-84e7-94dd77066b4b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_89e64fef-7d44-4c4f-8f52-7b82c49c540a" xlink:to="loc_us-gaap_SalesRevenueNetMember_5ac7fe2d-08db-43eb-84e7-94dd77066b4b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_f9331178-427c-4e6b-aba5-0dec46242e40" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_fb30e045-b853-49fd-9858-b7ec4af2e252" xlink:to="loc_srt_MajorCustomersAxis_f9331178-427c-4e6b-aba5-0dec46242e40" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_f9331178-427c-4e6b-aba5-0dec46242e40_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_f9331178-427c-4e6b-aba5-0dec46242e40" xlink:to="loc_srt_NameOfMajorCustomerDomain_f9331178-427c-4e6b-aba5-0dec46242e40_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_0780e065-ad05-46d2-8bee-c4c4aa95f127" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_f9331178-427c-4e6b-aba5-0dec46242e40" xlink:to="loc_srt_NameOfMajorCustomerDomain_0780e065-ad05-46d2-8bee-c4c4aa95f127" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_ChannelPartnersMember_81d5d1b3-0ed8-4764-a9de-aa9633a1966a" xlink:href="bsy-20220331.xsd#bsy_ChannelPartnersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_0780e065-ad05-46d2-8bee-c4c4aa95f127" xlink:to="loc_bsy_ChannelPartnersMember_81d5d1b3-0ed8-4764-a9de-aa9633a1966a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/RevenuefromContractswithCustomerPerformanceObligationDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#RevenuefromContractswithCustomerPerformanceObligationDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/RevenuefromContractswithCustomerPerformanceObligationDetails" xlink:type="extended" id="i12ad77d4873e4bf3acf710197a33bb7e_RevenuefromContractswithCustomerPerformanceObligationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_97897471-04bc-4757-aa56-110c2d3c06b0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_6c765613-5012-4c66-8545-8ec14dc5bfe9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_97897471-04bc-4757-aa56-110c2d3c06b0" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_6c765613-5012-4c66-8545-8ec14dc5bfe9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_010f318b-0743-4683-a04a-4b92aa152e4e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_97897471-04bc-4757-aa56-110c2d3c06b0" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_010f318b-0743-4683-a04a-4b92aa152e4e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_86eaf70f-f1f8-4113-b061-a1d171297a47" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_97897471-04bc-4757-aa56-110c2d3c06b0" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_86eaf70f-f1f8-4113-b061-a1d171297a47" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_08df2725-3d13-4029-8fd4-2a5da888292a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_97897471-04bc-4757-aa56-110c2d3c06b0" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_08df2725-3d13-4029-8fd4-2a5da888292a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_7322f89f-9f15-4a02-820b-42d93c5f23a5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_08df2725-3d13-4029-8fd4-2a5da888292a" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_7322f89f-9f15-4a02-820b-42d93c5f23a5" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/RevenuefromContractswithCustomerPerformanceObligationDetails_1" xlink:type="simple" xlink:href="bsy-20220331.xsd#RevenuefromContractswithCustomerPerformanceObligationDetails_1"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/RevenuefromContractswithCustomerPerformanceObligationDetails_1" xlink:type="extended" id="i3f541817c7574a47b6d344ec4d7a296f_RevenuefromContractswithCustomerPerformanceObligationDetails_1">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_97897471-04bc-4757-aa56-110c2d3c06b0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_6c765613-5012-4c66-8545-8ec14dc5bfe9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_97897471-04bc-4757-aa56-110c2d3c06b0" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_6c765613-5012-4c66-8545-8ec14dc5bfe9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_010f318b-0743-4683-a04a-4b92aa152e4e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_97897471-04bc-4757-aa56-110c2d3c06b0" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_010f318b-0743-4683-a04a-4b92aa152e4e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_86eaf70f-f1f8-4113-b061-a1d171297a47" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_97897471-04bc-4757-aa56-110c2d3c06b0" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_86eaf70f-f1f8-4113-b061-a1d171297a47" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_08df2725-3d13-4029-8fd4-2a5da888292a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_97897471-04bc-4757-aa56-110c2d3c06b0" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_08df2725-3d13-4029-8fd4-2a5da888292a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/RevenuefromContractswithCustomerScheduleofRevenueDisaggregationbyTypeDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#RevenuefromContractswithCustomerScheduleofRevenueDisaggregationbyTypeDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/RevenuefromContractswithCustomerScheduleofRevenueDisaggregationbyTypeDetails" xlink:type="extended" id="idbfa46dd3d4b4912a445a122cfffe84e_RevenuefromContractswithCustomerScheduleofRevenueDisaggregationbyTypeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_3ba60030-7767-467c-b54d-2811cb70419d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_e0e43d10-18de-4e09-85d2-39328e29310b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_3ba60030-7767-467c-b54d-2811cb70419d" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_e0e43d10-18de-4e09-85d2-39328e29310b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_2fdfe72a-b2f0-446a-b561-46ef3aed2723" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_3ba60030-7767-467c-b54d-2811cb70419d" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_2fdfe72a-b2f0-446a-b561-46ef3aed2723" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_a068794e-639f-44fa-93c1-376d34abfe6d" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_2fdfe72a-b2f0-446a-b561-46ef3aed2723" xlink:to="loc_srt_ProductOrServiceAxis_a068794e-639f-44fa-93c1-376d34abfe6d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_a068794e-639f-44fa-93c1-376d34abfe6d_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_a068794e-639f-44fa-93c1-376d34abfe6d" xlink:to="loc_srt_ProductsAndServicesDomain_a068794e-639f-44fa-93c1-376d34abfe6d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_e7ba263d-a659-4202-9990-1cdd3f1daa76" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_a068794e-639f-44fa-93c1-376d34abfe6d" xlink:to="loc_srt_ProductsAndServicesDomain_e7ba263d-a659-4202-9990-1cdd3f1daa76" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_SubscriptionsAndLicensesMember_d6501ea2-f5e3-4a2f-b37d-620444a0a70c" xlink:href="bsy-20220331.xsd#bsy_SubscriptionsAndLicensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_e7ba263d-a659-4202-9990-1cdd3f1daa76" xlink:to="loc_bsy_SubscriptionsAndLicensesMember_d6501ea2-f5e3-4a2f-b37d-620444a0a70c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubscriptionAndCirculationMember_c44a9055-54ba-446a-8d63-f3bd5cd77151" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubscriptionAndCirculationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_SubscriptionsAndLicensesMember_d6501ea2-f5e3-4a2f-b37d-620444a0a70c" xlink:to="loc_us-gaap_SubscriptionAndCirculationMember_c44a9055-54ba-446a-8d63-f3bd5cd77151" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_SELECTSubscriptionsMember_459d45a2-24a0-46e2-9794-75039f4ed406" xlink:href="bsy-20220331.xsd#bsy_SELECTSubscriptionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubscriptionAndCirculationMember_c44a9055-54ba-446a-8d63-f3bd5cd77151" xlink:to="loc_bsy_SELECTSubscriptionsMember_459d45a2-24a0-46e2-9794-75039f4ed406" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_EnterpriseLicenseSubscriptionsMember_d9863c18-2fcd-4fdd-9e38-d1b6a4eb55a5" xlink:href="bsy-20220331.xsd#bsy_EnterpriseLicenseSubscriptionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubscriptionAndCirculationMember_c44a9055-54ba-446a-8d63-f3bd5cd77151" xlink:to="loc_bsy_EnterpriseLicenseSubscriptionsMember_d9863c18-2fcd-4fdd-9e38-d1b6a4eb55a5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TermLicenseSubscriptionsMember_b6ff56a1-4cea-404f-9fc8-3f6e6947e3d2" xlink:href="bsy-20220331.xsd#bsy_TermLicenseSubscriptionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubscriptionAndCirculationMember_c44a9055-54ba-446a-8d63-f3bd5cd77151" xlink:to="loc_bsy_TermLicenseSubscriptionsMember_b6ff56a1-4cea-404f-9fc8-3f6e6947e3d2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_PerpetualLicensesMember_495bbf2e-529f-40f9-be27-9444a4dffc19" xlink:href="bsy-20220331.xsd#bsy_PerpetualLicensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_SubscriptionsAndLicensesMember_d6501ea2-f5e3-4a2f-b37d-620444a0a70c" xlink:to="loc_bsy_PerpetualLicensesMember_495bbf2e-529f-40f9-be27-9444a4dffc19" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceMember_a7e4021e-d682-4398-a75f-e182fd8440e0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_e7ba263d-a659-4202-9990-1cdd3f1daa76" xlink:to="loc_us-gaap_ServiceMember_a7e4021e-d682-4398-a75f-e182fd8440e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_ProfessionalServicesRecurringMember_20da001f-1513-4e87-ae51-c01910ffbb4a" xlink:href="bsy-20220331.xsd#bsy_ProfessionalServicesRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServiceMember_a7e4021e-d682-4398-a75f-e182fd8440e0" xlink:to="loc_bsy_ProfessionalServicesRecurringMember_20da001f-1513-4e87-ae51-c01910ffbb4a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_ProfessionalServicesOtherMember_1680a346-93f0-4b9e-a211-f52dfee75d2e" xlink:href="bsy-20220331.xsd#bsy_ProfessionalServicesOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServiceMember_a7e4021e-d682-4398-a75f-e182fd8440e0" xlink:to="loc_bsy_ProfessionalServicesOtherMember_1680a346-93f0-4b9e-a211-f52dfee75d2e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_EnterpriseLicenseSubscriptionsE365SubscriptionsMember_79b4e331-f135-4615-a453-c1f99bf02bd3" xlink:href="bsy-20220331.xsd#bsy_EnterpriseLicenseSubscriptionsE365SubscriptionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_e7ba263d-a659-4202-9990-1cdd3f1daa76" xlink:to="loc_bsy_EnterpriseLicenseSubscriptionsE365SubscriptionsMember_79b4e331-f135-4615-a453-c1f99bf02bd3" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/RevenuefromContractswithCustomerScheduleofRevenueDisaggregationbyLocationDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#RevenuefromContractswithCustomerScheduleofRevenueDisaggregationbyLocationDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/RevenuefromContractswithCustomerScheduleofRevenueDisaggregationbyLocationDetails" xlink:type="extended" id="id7afed4390bf48d19cf90612a23ea6b4_RevenuefromContractswithCustomerScheduleofRevenueDisaggregationbyLocationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_34f33f39-3f30-4dd4-8587-9e5bd663a8ee" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_e53c2863-d60f-473d-a602-e8a70abd2c95" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_34f33f39-3f30-4dd4-8587-9e5bd663a8ee" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_e53c2863-d60f-473d-a602-e8a70abd2c95" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_7728bde0-7ded-4664-ae48-b2a970b63a31" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_34f33f39-3f30-4dd4-8587-9e5bd663a8ee" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_7728bde0-7ded-4664-ae48-b2a970b63a31" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_50044ebc-33e5-45c3-bb57-53b07b9b1094" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_7728bde0-7ded-4664-ae48-b2a970b63a31" xlink:to="loc_srt_StatementGeographicalAxis_50044ebc-33e5-45c3-bb57-53b07b9b1094" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_50044ebc-33e5-45c3-bb57-53b07b9b1094_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_50044ebc-33e5-45c3-bb57-53b07b9b1094" xlink:to="loc_srt_SegmentGeographicalDomain_50044ebc-33e5-45c3-bb57-53b07b9b1094_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_9f6acfd3-0aac-4702-a197-685c8204c211" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_50044ebc-33e5-45c3-bb57-53b07b9b1094" xlink:to="loc_srt_SegmentGeographicalDomain_9f6acfd3-0aac-4702-a197-685c8204c211" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_UnitedStatesCanadaAndLatinAmericaMember_28e78ffd-74f9-406d-a777-72d7b1237e5a" xlink:href="bsy-20220331.xsd#bsy_UnitedStatesCanadaAndLatinAmericaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_9f6acfd3-0aac-4702-a197-685c8204c211" xlink:to="loc_bsy_UnitedStatesCanadaAndLatinAmericaMember_28e78ffd-74f9-406d-a777-72d7b1237e5a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_176ff975-2407-4c66-bcb6-8573a9de8530" xlink:href="https://xbrl.sec.gov/country/2021/country-2021.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_UnitedStatesCanadaAndLatinAmericaMember_28e78ffd-74f9-406d-a777-72d7b1237e5a" xlink:to="loc_country_US_176ff975-2407-4c66-bcb6-8573a9de8530" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EMEAMember_d4e9d093-1822-44dd-b285-8179ac7ffee0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EMEAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_9f6acfd3-0aac-4702-a197-685c8204c211" xlink:to="loc_us-gaap_EMEAMember_d4e9d093-1822-44dd-b285-8179ac7ffee0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_GB_fc7d6f64-6de7-4ecc-bd4b-56fc814ffec3" xlink:href="https://xbrl.sec.gov/country/2021/country-2021.xsd#country_GB"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EMEAMember_d4e9d093-1822-44dd-b285-8179ac7ffee0" xlink:to="loc_country_GB_fc7d6f64-6de7-4ecc-bd4b-56fc814ffec3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AsiaPacificMember_b8c9f4ae-ab20-455f-81bd-8bad1080c596" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_AsiaPacificMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_9f6acfd3-0aac-4702-a197-685c8204c211" xlink:to="loc_srt_AsiaPacificMember_b8c9f4ae-ab20-455f-81bd-8bad1080c596" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/AcquisitionsNarrativeDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#AcquisitionsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/AcquisitionsNarrativeDetails" xlink:type="extended" id="id7d3e707cc5f4adcb6b74daa6af5e354_AcquisitionsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_6eaa80d1-7cac-408f-8322-4aff05bbcac8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_500a3c1c-1d6d-41b8-af37-11d0e30e41de" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_6eaa80d1-7cac-408f-8322-4aff05bbcac8" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_500a3c1c-1d6d-41b8-af37-11d0e30e41de" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_a9244350-bc33-4558-be6b-6350323173f8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_6eaa80d1-7cac-408f-8322-4aff05bbcac8" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_a9244350-bc33-4558-be6b-6350323173f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_c2a5b2aa-70fd-43d6-b716-c5cff30811be" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_6eaa80d1-7cac-408f-8322-4aff05bbcac8" xlink:to="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_c2a5b2aa-70fd-43d6-b716-c5cff30811be" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsAdditionalDisclosuresAcquisitionCostExpensed_fb89bf58-bb9d-49bb-b25e-828a294a54bd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsAdditionalDisclosuresAcquisitionCostExpensed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_6eaa80d1-7cac-408f-8322-4aff05bbcac8" xlink:to="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsAdditionalDisclosuresAcquisitionCostExpensed_fb89bf58-bb9d-49bb-b25e-828a294a54bd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount_ad3eb6f6-13d8-4d35-9b2d-6cdf0fd8abb7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_6eaa80d1-7cac-408f-8322-4aff05bbcac8" xlink:to="loc_us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount_ad3eb6f6-13d8-4d35-9b2d-6cdf0fd8abb7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionsProFormaRevenue_114fed1f-7b0a-4a16-a574-14c12c73646b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionsProFormaRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_6eaa80d1-7cac-408f-8322-4aff05bbcac8" xlink:to="loc_us-gaap_BusinessAcquisitionsProFormaRevenue_114fed1f-7b0a-4a16-a574-14c12c73646b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfBusinessesAcquired_bcafb946-1eff-43b4-b717-03fc7b887c47" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NumberOfBusinessesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_6eaa80d1-7cac-408f-8322-4aff05bbcac8" xlink:to="loc_us-gaap_NumberOfBusinessesAcquired_bcafb946-1eff-43b4-b717-03fc7b887c47" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable_023b4936-4496-49f1-b474-043c3aa0cb27" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_6eaa80d1-7cac-408f-8322-4aff05bbcac8" xlink:to="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable_023b4936-4496-49f1-b474-043c3aa0cb27" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_7ba84450-f44d-40df-a4c6-ee7cad9843b0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable_023b4936-4496-49f1-b474-043c3aa0cb27" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_7ba84450-f44d-40df-a4c6-ee7cad9843b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7ba84450-f44d-40df-a4c6-ee7cad9843b0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_7ba84450-f44d-40df-a4c6-ee7cad9843b0" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7ba84450-f44d-40df-a4c6-ee7cad9843b0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_8f08e11c-ab64-41f3-b959-d14808dcb1b8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_7ba84450-f44d-40df-a4c6-ee7cad9843b0" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_8f08e11c-ab64-41f3-b959-d14808dcb1b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_PowerLineSystemsAcquisitionMember_3c1a2dd3-e62c-46ef-892b-aba5e8fa8c88" xlink:href="bsy-20220331.xsd#bsy_PowerLineSystemsAcquisitionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_8f08e11c-ab64-41f3-b959-d14808dcb1b8" xlink:to="loc_bsy_PowerLineSystemsAcquisitionMember_3c1a2dd3-e62c-46ef-892b-aba5e8fa8c88" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember_cba5069d-a4b8-47fb-b5aa-b7b9478cb334" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_8f08e11c-ab64-41f3-b959-d14808dcb1b8" xlink:to="loc_us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember_cba5069d-a4b8-47fb-b5aa-b7b9478cb334" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_SeequentMember_544d8a15-df3b-4a54-9b2c-8198a2696995" xlink:href="bsy-20220331.xsd#bsy_SeequentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_8f08e11c-ab64-41f3-b959-d14808dcb1b8" xlink:to="loc_bsy_SeequentMember_544d8a15-df3b-4a54-9b2c-8198a2696995" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_4081564e-8c18-4f81-8471-f9b1eb276d93" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable_023b4936-4496-49f1-b474-043c3aa0cb27" xlink:to="loc_us-gaap_StatementClassOfStockAxis_4081564e-8c18-4f81-8471-f9b1eb276d93" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_4081564e-8c18-4f81-8471-f9b1eb276d93_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_4081564e-8c18-4f81-8471-f9b1eb276d93" xlink:to="loc_us-gaap_ClassOfStockDomain_4081564e-8c18-4f81-8471-f9b1eb276d93_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_185b0641-ec11-49cd-b1c7-7adb06bd439a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_4081564e-8c18-4f81-8471-f9b1eb276d93" xlink:to="loc_us-gaap_ClassOfStockDomain_185b0641-ec11-49cd-b1c7-7adb06bd439a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_90ff5b52-47e1-44cd-8a07-245e0208d2ff" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_185b0641-ec11-49cd-b1c7-7adb06bd439a" xlink:to="loc_us-gaap_CommonClassBMember_90ff5b52-47e1-44cd-8a07-245e0208d2ff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_c79f401e-a8d6-42a1-a43f-470df20cd0c1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable_023b4936-4496-49f1-b474-043c3aa0cb27" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_c79f401e-a8d6-42a1-a43f-470df20cd0c1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_c79f401e-a8d6-42a1-a43f-470df20cd0c1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_c79f401e-a8d6-42a1-a43f-470df20cd0c1" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_c79f401e-a8d6-42a1-a43f-470df20cd0c1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_af8d722e-8738-4774-a0bd-f50d82ac591c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_c79f401e-a8d6-42a1-a43f-470df20cd0c1" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_af8d722e-8738-4774-a0bd-f50d82ac591c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_4e02b95a-6769-4185-beab-ebfb16f0f7ba" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_af8d722e-8738-4774-a0bd-f50d82ac591c" xlink:to="loc_us-gaap_SubsequentEventMember_4e02b95a-6769-4185-beab-ebfb16f0f7ba" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/AcquisitionsScheduleofCashPaidandAcquiredforAcquisitionsDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#AcquisitionsScheduleofCashPaidandAcquiredforAcquisitionsDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/AcquisitionsScheduleofCashPaidandAcquiredforAcquisitionsDetails" xlink:type="extended" id="ic4d959ed0cdf4d28b3192c0311552a33_AcquisitionsScheduleofCashPaidandAcquiredforAcquisitionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_41650641-e1cf-4c0c-a67e-2d48562912a9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfBusinessesAcquired_ffee0232-f4cd-4ca9-97ed-0cdf9b5d0eff" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NumberOfBusinessesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_41650641-e1cf-4c0c-a67e-2d48562912a9" xlink:to="loc_us-gaap_NumberOfBusinessesAcquired_ffee0232-f4cd-4ca9-97ed-0cdf9b5d0eff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_9e47c4af-edb4-489a-b722-27a09804b086" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_41650641-e1cf-4c0c-a67e-2d48562912a9" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_9e47c4af-edb4-489a-b722-27a09804b086" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAcquiredFromAcquisition_22dbabfb-95e8-4c07-a7d0-87959b39cae1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAcquiredFromAcquisition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_41650641-e1cf-4c0c-a67e-2d48562912a9" xlink:to="loc_us-gaap_CashAcquiredFromAcquisition_22dbabfb-95e8-4c07-a7d0-87959b39cae1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_2d1307ec-44e1-4580-9e09-d5eeed668dd3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_41650641-e1cf-4c0c-a67e-2d48562912a9" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_2d1307ec-44e1-4580-9e09-d5eeed668dd3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EscrowDeposit_5de8e503-ca5d-40b4-b61e-42e1b40805d4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EscrowDeposit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_41650641-e1cf-4c0c-a67e-2d48562912a9" xlink:to="loc_us-gaap_EscrowDeposit_5de8e503-ca5d-40b4-b61e-42e1b40805d4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable_12d8b61d-c702-46c6-8c24-1030e5f54941" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_41650641-e1cf-4c0c-a67e-2d48562912a9" xlink:to="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable_12d8b61d-c702-46c6-8c24-1030e5f54941" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_04fbca57-ad10-481f-960f-49ec430e4fa1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable_12d8b61d-c702-46c6-8c24-1030e5f54941" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_04fbca57-ad10-481f-960f-49ec430e4fa1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_04fbca57-ad10-481f-960f-49ec430e4fa1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_04fbca57-ad10-481f-960f-49ec430e4fa1" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_04fbca57-ad10-481f-960f-49ec430e4fa1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d96d1fa1-5ed3-475b-8096-7b1ecf428cdf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_04fbca57-ad10-481f-960f-49ec430e4fa1" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d96d1fa1-5ed3-475b-8096-7b1ecf428cdf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember_24cffb78-b8a6-4126-a16b-c86c5aa6ccb0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d96d1fa1-5ed3-475b-8096-7b1ecf428cdf" xlink:to="loc_us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember_24cffb78-b8a6-4126-a16b-c86c5aa6ccb0" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/AcquisitionsScheduleofContingentandNonContingentConsiderationFairValueDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#AcquisitionsScheduleofContingentandNonContingentConsiderationFairValueDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/AcquisitionsScheduleofContingentandNonContingentConsiderationFairValueDetails" xlink:type="extended" id="i04e48cc6de064b4bbcb6e9725d2fa940_AcquisitionsScheduleofContingentandNonContingentConsiderationFairValueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_2a1ed2d7-c39c-4b41-8f58-199612013f4a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionContingentConsiderationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_c129bf5f-0d4f-47a0-8313-cbc8899ae19e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_2a1ed2d7-c39c-4b41-8f58-199612013f4a" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_c129bf5f-0d4f-47a0-8313-cbc8899ae19e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent_418b8ba0-f388-4b49-82d0-f57261f00e0f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_2a1ed2d7-c39c-4b41-8f58-199612013f4a" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent_418b8ba0-f388-4b49-82d0-f57261f00e0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_73d150db-24d7-48c2-b9cc-7f4d3a78dd8a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_2a1ed2d7-c39c-4b41-8f58-199612013f4a" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_73d150db-24d7-48c2-b9cc-7f4d3a78dd8a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_BusinessCombinationConsiderationPayableCurrent_a9e5a48a-b918-4eea-a73e-e17e39cf9da5" xlink:href="bsy-20220331.xsd#bsy_BusinessCombinationConsiderationPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_2a1ed2d7-c39c-4b41-8f58-199612013f4a" xlink:to="loc_bsy_BusinessCombinationConsiderationPayableCurrent_a9e5a48a-b918-4eea-a73e-e17e39cf9da5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_BusinessCombinationConsiderationPayableNoncurrent_581cb466-8ac9-4d5b-b9c9-b671e334052a" xlink:href="bsy-20220331.xsd#bsy_BusinessCombinationConsiderationPayableNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_2a1ed2d7-c39c-4b41-8f58-199612013f4a" xlink:to="loc_bsy_BusinessCombinationConsiderationPayableNoncurrent_581cb466-8ac9-4d5b-b9c9-b671e334052a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_BusinessCombinationConsiderationPayable_37c67bb9-c38c-4b78-8ecc-25b6cfce56ef" xlink:href="bsy-20220331.xsd#bsy_BusinessCombinationConsiderationPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_2a1ed2d7-c39c-4b41-8f58-199612013f4a" xlink:to="loc_bsy_BusinessCombinationConsiderationPayable_37c67bb9-c38c-4b78-8ecc-25b6cfce56ef" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_66a45f3f-a6c4-4c38-9d18-c354f4314fe1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_2a1ed2d7-c39c-4b41-8f58-199612013f4a" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_66a45f3f-a6c4-4c38-9d18-c354f4314fe1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_59b02d73-89cd-4fa6-82cc-220f94f5d871" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_66a45f3f-a6c4-4c38-9d18-c354f4314fe1" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_59b02d73-89cd-4fa6-82cc-220f94f5d871" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_59b02d73-89cd-4fa6-82cc-220f94f5d871_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_59b02d73-89cd-4fa6-82cc-220f94f5d871" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_59b02d73-89cd-4fa6-82cc-220f94f5d871_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3c544e74-7d38-463a-a736-c0033f647756" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_59b02d73-89cd-4fa6-82cc-220f94f5d871" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3c544e74-7d38-463a-a736-c0033f647756" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember_7ea4659a-b7af-4489-bac0-cd1de60118a0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3c544e74-7d38-463a-a736-c0033f647756" xlink:to="loc_us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember_7ea4659a-b7af-4489-bac0-cd1de60118a0" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/AcquisitionsScheduleofConsiderationandNetAssetsAcquiredDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#AcquisitionsScheduleofConsiderationandNetAssetsAcquiredDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/AcquisitionsScheduleofConsiderationandNetAssetsAcquiredDetails" xlink:type="extended" id="i220e6eac9ff14fef97a035ea5dbcdfaa_AcquisitionsScheduleofConsiderationandNetAssetsAcquiredDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_5099f9b7-d1cd-475a-8d29-851efe9ade77" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_eecbed3d-27ba-4b8b-a8ff-6aaf05609bc9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_5099f9b7-d1cd-475a-8d29-851efe9ade77" xlink:to="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_eecbed3d-27ba-4b8b-a8ff-6aaf05609bc9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_76666c72-ab6d-4e6e-918b-bb816489a427" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_5099f9b7-d1cd-475a-8d29-851efe9ade77" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_76666c72-ab6d-4e6e-918b-bb816489a427" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_ce707436-b5b9-43e4-ac2a-504d22a302ab" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_5099f9b7-d1cd-475a-8d29-851efe9ade77" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_ce707436-b5b9-43e4-ac2a-504d22a302ab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_BusinessCombinationContingentConsiderationLiabilityInitialValue_1f764b21-2300-4361-a1ea-ec068453728b" xlink:href="bsy-20220331.xsd#bsy_BusinessCombinationContingentConsiderationLiabilityInitialValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_5099f9b7-d1cd-475a-8d29-851efe9ade77" xlink:to="loc_bsy_BusinessCombinationContingentConsiderationLiabilityInitialValue_1f764b21-2300-4361-a1ea-ec068453728b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_BusinessCombinationConsiderationPayableInitialValue_3f5330ed-3952-4b2c-8ef5-4e84d3bafbc9" xlink:href="bsy-20220331.xsd#bsy_BusinessCombinationConsiderationPayableInitialValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_5099f9b7-d1cd-475a-8d29-851efe9ade77" xlink:to="loc_bsy_BusinessCombinationConsiderationPayableInitialValue_3f5330ed-3952-4b2c-8ef5-4e84d3bafbc9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_71762380-7f0e-4c07-beaa-4b27cc7a7943" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_5099f9b7-d1cd-475a-8d29-851efe9ade77" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_71762380-7f0e-4c07-beaa-4b27cc7a7943" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_5099f9b7-d1cd-475a-8d29-851efe9ade77" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_e30f9908-2bd2-400a-aef8-c12e9cdd3636" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_e30f9908-2bd2-400a-aef8-c12e9cdd3636" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivablesAndOtherCurrentAssets_b17441c0-570b-483e-8e9e-e5320675bd08" xlink:href="bsy-20220331.xsd#bsy_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivablesAndOtherCurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:to="loc_bsy_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivablesAndOtherCurrentAssets_b17441c0-570b-483e-8e9e-e5320675bd08" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentAssetsOperatingLeaseRightOfUseAsset_73da9a35-1d61-473f-bbc9-350c056b62fa" xlink:href="bsy-20220331.xsd#bsy_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentAssetsOperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:to="loc_bsy_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentAssetsOperatingLeaseRightOfUseAsset_73da9a35-1d61-473f-bbc9-350c056b62fa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_d8b69c5b-f840-4e46-8661-77acd4ca2051" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_d8b69c5b-f840-4e46-8661-77acd4ca2051" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_be5fa777-e245-438a-9f97-08c7eba47863" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_be5fa777-e245-438a-9f97-08c7eba47863" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_a7c2c11d-b38f-4093-88aa-9041263d9335" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_a7c2c11d-b38f-4093-88aa-9041263d9335" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_f2e4a0f9-202a-43fa-a2c5-447367b0295c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_f2e4a0f9-202a-43fa-a2c5-447367b0295c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_182240f8-8880-483f-8738-a97bd58e3491" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_182240f8-8880-483f-8738-a97bd58e3491" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesDeferredRevenue_4d4899ee-b091-46e9-a488-6529953918a0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesDeferredRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesDeferredRevenue_4d4899ee-b091-46e9-a488-6529953918a0" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOperatingLeaseLiabilityNoncurrent_fcc797a8-f448-485f-bf37-835e450b43e8" xlink:href="bsy-20220331.xsd#bsy_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:to="loc_bsy_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOperatingLeaseLiabilityNoncurrent_fcc797a8-f448-485f-bf37-835e450b43e8" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_e391b8c3-8309-4e5e-aab3-e23502f3da7e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_e391b8c3-8309-4e5e-aab3-e23502f3da7e" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_5b6bbe59-a9cf-4f7c-b1e5-6029e6aa22fc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_5b6bbe59-a9cf-4f7c-b1e5-6029e6aa22fc" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_a831d83f-c499-4ce6-9164-1716d5ba0928" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_a831d83f-c499-4ce6-9164-1716d5ba0928" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_dd9e55af-2502-4222-8662-b4a3e4125e25" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_dd9e55af-2502-4222-8662-b4a3e4125e25" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_08329f78-75fd-49e1-9b47-183195574765" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:to="loc_us-gaap_Goodwill_08329f78-75fd-49e1-9b47-183195574765" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_e7076bca-c0a4-4a25-a360-0146a154366a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_5c1184d2-1ac3-4055-9d47-60ed80f75283" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_e7076bca-c0a4-4a25-a360-0146a154366a" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_4bb05b2c-0c35-4fe4-9c3c-29d869705fa5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_5099f9b7-d1cd-475a-8d29-851efe9ade77" xlink:to="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_4bb05b2c-0c35-4fe4-9c3c-29d869705fa5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_SaleOfStockNumberOfSharesIssuedInTransactionSubjectToEmploymentServiceConditions_0f31c06a-c93c-49d8-a73a-a081a918ea9c" xlink:href="bsy-20220331.xsd#bsy_SaleOfStockNumberOfSharesIssuedInTransactionSubjectToEmploymentServiceConditions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_5099f9b7-d1cd-475a-8d29-851efe9ade77" xlink:to="loc_bsy_SaleOfStockNumberOfSharesIssuedInTransactionSubjectToEmploymentServiceConditions_0f31c06a-c93c-49d8-a73a-a081a918ea9c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_048d2d3b-a8e1-408a-8b64-54c9c54cea8d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_5099f9b7-d1cd-475a-8d29-851efe9ade77" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_048d2d3b-a8e1-408a-8b64-54c9c54cea8d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1_9e904601-bfed-4e4c-9827-b1d99efc94b2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_5099f9b7-d1cd-475a-8d29-851efe9ade77" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1_9e904601-bfed-4e4c-9827-b1d99efc94b2" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentEquityInterests_ac4455cb-dbff-48ec-baff-f3718e56c327" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentEquityInterests"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_5099f9b7-d1cd-475a-8d29-851efe9ade77" xlink:to="loc_us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentEquityInterests_ac4455cb-dbff-48ec-baff-f3718e56c327" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable_ffae3291-02ef-4fcc-95b3-17881e485005" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsLineItems_5099f9b7-d1cd-475a-8d29-851efe9ade77" xlink:to="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable_ffae3291-02ef-4fcc-95b3-17881e485005" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_97fe5c56-6b7e-42ef-aafc-421c4a3cec9b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable_ffae3291-02ef-4fcc-95b3-17881e485005" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_97fe5c56-6b7e-42ef-aafc-421c4a3cec9b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_97fe5c56-6b7e-42ef-aafc-421c4a3cec9b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_97fe5c56-6b7e-42ef-aafc-421c4a3cec9b" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_97fe5c56-6b7e-42ef-aafc-421c4a3cec9b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_304e36ab-8ff5-47d2-8ba3-b137420fdc45" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_97fe5c56-6b7e-42ef-aafc-421c4a3cec9b" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_304e36ab-8ff5-47d2-8ba3-b137420fdc45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember_fb667d42-5710-40ae-a0ea-72ec58c2d221" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_304e36ab-8ff5-47d2-8ba3-b137420fdc45" xlink:to="loc_us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember_fb667d42-5710-40ae-a0ea-72ec58c2d221" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_SeequentMember_81bf210b-72a6-4850-a8ea-8a28d2574d67" xlink:href="bsy-20220331.xsd#bsy_SeequentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_304e36ab-8ff5-47d2-8ba3-b137420fdc45" xlink:to="loc_bsy_SeequentMember_81bf210b-72a6-4850-a8ea-8a28d2574d67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_21df8da5-3857-4d2a-884a-550e22b60d42" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable_ffae3291-02ef-4fcc-95b3-17881e485005" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_21df8da5-3857-4d2a-884a-550e22b60d42" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_21df8da5-3857-4d2a-884a-550e22b60d42_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_21df8da5-3857-4d2a-884a-550e22b60d42" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_21df8da5-3857-4d2a-884a-550e22b60d42_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9c140c71-8f47-4680-8fca-4e3b5d208989" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_21df8da5-3857-4d2a-884a-550e22b60d42" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9c140c71-8f47-4680-8fca-4e3b5d208989" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_085014ea-9996-4543-826f-dee05ae7a18b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ComputerSoftwareIntangibleAssetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9c140c71-8f47-4680-8fca-4e3b5d208989" xlink:to="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_085014ea-9996-4543-826f-dee05ae7a18b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_debd0bd7-83cc-417e-8cf2-abe972f86709" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9c140c71-8f47-4680-8fca-4e3b5d208989" xlink:to="loc_us-gaap_CustomerRelationshipsMember_debd0bd7-83cc-417e-8cf2-abe972f86709" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksMember_5a01f967-f628-410c-a27e-fff53b85eb2a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TrademarksMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9c140c71-8f47-4680-8fca-4e3b5d208989" xlink:to="loc_us-gaap_TrademarksMember_5a01f967-f628-410c-a27e-fff53b85eb2a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InProcessResearchAndDevelopmentMember_09982b7d-5a09-4de1-8b24-fe0a55a1451e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InProcessResearchAndDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9c140c71-8f47-4680-8fca-4e3b5d208989" xlink:to="loc_us-gaap_InProcessResearchAndDevelopmentMember_09982b7d-5a09-4de1-8b24-fe0a55a1451e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_590d8c54-78ae-44fc-a2e5-6c85cc1cecf6" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable_ffae3291-02ef-4fcc-95b3-17881e485005" xlink:to="loc_srt_RangeAxis_590d8c54-78ae-44fc-a2e5-6c85cc1cecf6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_590d8c54-78ae-44fc-a2e5-6c85cc1cecf6_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_590d8c54-78ae-44fc-a2e5-6c85cc1cecf6" xlink:to="loc_srt_RangeMember_590d8c54-78ae-44fc-a2e5-6c85cc1cecf6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_109c1717-9c52-458e-af8e-7eef26536ac9" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_590d8c54-78ae-44fc-a2e5-6c85cc1cecf6" xlink:to="loc_srt_RangeMember_109c1717-9c52-458e-af8e-7eef26536ac9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_WeightedAverageMember_632c2e19-9506-48c1-bf33-d3b63c03042a" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_WeightedAverageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_109c1717-9c52-458e-af8e-7eef26536ac9" xlink:to="loc_srt_WeightedAverageMember_632c2e19-9506-48c1-bf33-d3b63c03042a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_f7868bd6-6165-4bb0-ac0e-2c11da5b29d0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable_ffae3291-02ef-4fcc-95b3-17881e485005" xlink:to="loc_us-gaap_StatementClassOfStockAxis_f7868bd6-6165-4bb0-ac0e-2c11da5b29d0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_f7868bd6-6165-4bb0-ac0e-2c11da5b29d0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_f7868bd6-6165-4bb0-ac0e-2c11da5b29d0" xlink:to="loc_us-gaap_ClassOfStockDomain_f7868bd6-6165-4bb0-ac0e-2c11da5b29d0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_f07edc4f-388a-4b8c-8b2a-ee9853bc9179" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_f7868bd6-6165-4bb0-ac0e-2c11da5b29d0" xlink:to="loc_us-gaap_ClassOfStockDomain_f07edc4f-388a-4b8c-8b2a-ee9853bc9179" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_db78e9b9-7b33-4aa7-89e9-bf1e6363f419" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_f07edc4f-388a-4b8c-8b2a-ee9853bc9179" xlink:to="loc_us-gaap_CommonClassBMember_db78e9b9-7b33-4aa7-89e9-bf1e6363f419" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_af0056a0-2b59-4527-966d-d358e1de4ad7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsTable_ffae3291-02ef-4fcc-95b3-17881e485005" xlink:to="loc_us-gaap_AwardTypeAxis_af0056a0-2b59-4527-966d-d358e1de4ad7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_af0056a0-2b59-4527-966d-d358e1de4ad7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_af0056a0-2b59-4527-966d-d358e1de4ad7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_af0056a0-2b59-4527-966d-d358e1de4ad7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_65d0c835-0c4c-4abe-a707-3dd5a88bbc07" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_af0056a0-2b59-4527-966d-d358e1de4ad7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_65d0c835-0c4c-4abe-a707-3dd5a88bbc07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_CommonClassBStockSubjectToServiceConditionsMember_113e5593-efe5-4f81-b9b6-26cc5cf71431" xlink:href="bsy-20220331.xsd#bsy_CommonClassBStockSubjectToServiceConditionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_65d0c835-0c4c-4abe-a707-3dd5a88bbc07" xlink:to="loc_bsy_CommonClassBStockSubjectToServiceConditionsMember_113e5593-efe5-4f81-b9b6-26cc5cf71431" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/PropertyandEquipmentNetScheduleofPropertyandEquipmentNetDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#PropertyandEquipmentNetScheduleofPropertyandEquipmentNetDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/PropertyandEquipmentNetScheduleofPropertyandEquipmentNetDetails" xlink:type="extended" id="icf1e36ea88e241a09ec6ec56a0332865_PropertyandEquipmentNetScheduleofPropertyandEquipmentNetDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_0758f949-a56b-40f2-9881-c19b29b5273f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_ea96afe2-d76b-48cd-9c34-a2d89c08c573" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_0758f949-a56b-40f2-9881-c19b29b5273f" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_ea96afe2-d76b-48cd-9c34-a2d89c08c573" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_170c0439-b6a1-4a01-a76e-3723b2a07873" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_0758f949-a56b-40f2-9881-c19b29b5273f" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_170c0439-b6a1-4a01-a76e-3723b2a07873" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_caa4d16e-b762-4109-87fc-a3c774bea29a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_0758f949-a56b-40f2-9881-c19b29b5273f" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_caa4d16e-b762-4109-87fc-a3c774bea29a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_d5752f08-185b-4894-ad41-bec58c219534" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_0758f949-a56b-40f2-9881-c19b29b5273f" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_d5752f08-185b-4894-ad41-bec58c219534" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_366ac994-1bda-4fa6-b03b-0bdb39a3faa0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_d5752f08-185b-4894-ad41-bec58c219534" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_366ac994-1bda-4fa6-b03b-0bdb39a3faa0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_366ac994-1bda-4fa6-b03b-0bdb39a3faa0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_366ac994-1bda-4fa6-b03b-0bdb39a3faa0" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_366ac994-1bda-4fa6-b03b-0bdb39a3faa0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_74d37878-2472-4883-a3c6-4df79bad7f3c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_366ac994-1bda-4fa6-b03b-0bdb39a3faa0" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_74d37878-2472-4883-a3c6-4df79bad7f3c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandMember_7ed1f37a-a544-416f-af04-8ec5732833a5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LandMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_74d37878-2472-4883-a3c6-4df79bad7f3c" xlink:to="loc_us-gaap_LandMember_7ed1f37a-a544-416f-af04-8ec5732833a5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BuildingAndBuildingImprovementsMember_6e799c30-39b0-42da-a7de-14794424fb36" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BuildingAndBuildingImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_74d37878-2472-4883-a3c6-4df79bad7f3c" xlink:to="loc_us-gaap_BuildingAndBuildingImprovementsMember_6e799c30-39b0-42da-a7de-14794424fb36" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_ComputerEquipmentAndSoftwareMember_fd40f831-10b5-4940-a730-9549920a30aa" xlink:href="bsy-20220331.xsd#bsy_ComputerEquipmentAndSoftwareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_74d37878-2472-4883-a3c6-4df79bad7f3c" xlink:to="loc_bsy_ComputerEquipmentAndSoftwareMember_fd40f831-10b5-4940-a730-9549920a30aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_133335bf-1bd0-4abd-a4ff-a604ea9c5c69" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FurnitureAndFixturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_74d37878-2472-4883-a3c6-4df79bad7f3c" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_133335bf-1bd0-4abd-a4ff-a604ea9c5c69" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AirTransportationEquipmentMember_ce75d24c-c46e-42a4-b0eb-702ba981a1b9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AirTransportationEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_74d37878-2472-4883-a3c6-4df79bad7f3c" xlink:to="loc_us-gaap_AirTransportationEquipmentMember_ce75d24c-c46e-42a4-b0eb-702ba981a1b9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCapitalizedPropertyPlantAndEquipmentMember_3e60885f-8b11-487c-b470-9e4e95dde672" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherCapitalizedPropertyPlantAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_74d37878-2472-4883-a3c6-4df79bad7f3c" xlink:to="loc_us-gaap_OtherCapitalizedPropertyPlantAndEquipmentMember_3e60885f-8b11-487c-b470-9e4e95dde672" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/PropertyandEquipmentNetNarrativeDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#PropertyandEquipmentNetNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/PropertyandEquipmentNetNarrativeDetails" xlink:type="extended" id="id546c410b5324e74bef6c76cd92d41b9_PropertyandEquipmentNetNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_46ab5430-b6f0-495d-9040-5a7e5267eda6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationNonproduction_9630f8de-c634-4d44-9df2-87a786619e1b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DepreciationNonproduction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_46ab5430-b6f0-495d-9040-5a7e5267eda6" xlink:to="loc_us-gaap_DepreciationNonproduction_9630f8de-c634-4d44-9df2-87a786619e1b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_SaleOfInterestInPropertyPlantEquipmentPercent_94cb4a83-b7cf-47c4-bfcd-b05448f94c6e" xlink:href="bsy-20220331.xsd#bsy_SaleOfInterestInPropertyPlantEquipmentPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_46ab5430-b6f0-495d-9040-5a7e5267eda6" xlink:to="loc_bsy_SaleOfInterestInPropertyPlantEquipmentPercent_94cb4a83-b7cf-47c4-bfcd-b05448f94c6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_f74362f3-3525-46bc-b25f-7645cd07c801" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_46ab5430-b6f0-495d-9040-5a7e5267eda6" xlink:to="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_f74362f3-3525-46bc-b25f-7645cd07c801" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_f2df2d31-3ba7-42ca-a978-9eff7dc146d3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_46ab5430-b6f0-495d-9040-5a7e5267eda6" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_f2df2d31-3ba7-42ca-a978-9eff7dc146d3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_0dddd29e-5260-46d5-879d-dcb036334640" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_46ab5430-b6f0-495d-9040-5a7e5267eda6" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_0dddd29e-5260-46d5-879d-dcb036334640" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_0f5f1657-2eb8-4d72-b33f-af95d364b30a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_0dddd29e-5260-46d5-879d-dcb036334640" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_0f5f1657-2eb8-4d72-b33f-af95d364b30a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_0f5f1657-2eb8-4d72-b33f-af95d364b30a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_0f5f1657-2eb8-4d72-b33f-af95d364b30a" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_0f5f1657-2eb8-4d72-b33f-af95d364b30a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e9247508-4406-4bdb-b515-34de4ff1443a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_0f5f1657-2eb8-4d72-b33f-af95d364b30a" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e9247508-4406-4bdb-b515-34de4ff1443a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AirTransportationEquipmentMember_ce65213d-bf98-4932-a746-cfce5889aa46" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AirTransportationEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e9247508-4406-4bdb-b515-34de4ff1443a" xlink:to="loc_us-gaap_AirTransportationEquipmentMember_ce65213d-bf98-4932-a746-cfce5889aa46" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_09951fdb-8e97-4310-afab-83eb42fb6248" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_0dddd29e-5260-46d5-879d-dcb036334640" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_09951fdb-8e97-4310-afab-83eb42fb6248" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_09951fdb-8e97-4310-afab-83eb42fb6248_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_09951fdb-8e97-4310-afab-83eb42fb6248" xlink:to="loc_us-gaap_RelatedPartyDomain_09951fdb-8e97-4310-afab-83eb42fb6248_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_752c16c9-09b7-44f0-b371-71631639d4a7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_09951fdb-8e97-4310-afab-83eb42fb6248" xlink:to="loc_us-gaap_RelatedPartyDomain_752c16c9-09b7-44f0-b371-71631639d4a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_EntityControlledByCEOMember_c0379a1e-0ed2-460d-aed0-7e42cdf2b696" xlink:href="bsy-20220331.xsd#bsy_EntityControlledByCEOMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_752c16c9-09b7-44f0-b371-71631639d4a7" xlink:to="loc_bsy_EntityControlledByCEOMember_c0379a1e-0ed2-460d-aed0-7e42cdf2b696" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/GoodwillandOtherIntangibleAssetsIntangibleAssetsOtherthanGoodwillDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#GoodwillandOtherIntangibleAssetsIntangibleAssetsOtherthanGoodwillDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/GoodwillandOtherIntangibleAssetsIntangibleAssetsOtherthanGoodwillDetails" xlink:type="extended" id="i46d27e90402b4aaab928625c274ea453_GoodwillandOtherIntangibleAssetsIntangibleAssetsOtherthanGoodwillDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_855bc3de-bc17-4308-bddd-f609dd3bade6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_12dfa116-b1e6-4f10-8296-fe73e2bfb505" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNetAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_855bc3de-bc17-4308-bddd-f609dd3bade6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_12dfa116-b1e6-4f10-8296-fe73e2bfb505" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_44625cdc-e8a5-4b3b-a7a3-86fc9831c17b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_12dfa116-b1e6-4f10-8296-fe73e2bfb505" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_44625cdc-e8a5-4b3b-a7a3-86fc9831c17b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_27333e84-17a7-4069-90a4-d1be27f0f878" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_12dfa116-b1e6-4f10-8296-fe73e2bfb505" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_27333e84-17a7-4069-90a4-d1be27f0f878" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_4cf954ec-b37f-4eab-9c7c-69487b4dfc85" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_12dfa116-b1e6-4f10-8296-fe73e2bfb505" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_4cf954ec-b37f-4eab-9c7c-69487b4dfc85" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_bb004443-1509-4733-a02e-d0f947796550" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_12dfa116-b1e6-4f10-8296-fe73e2bfb505" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_bb004443-1509-4733-a02e-d0f947796550" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_b2101ef0-4386-42af-8ea2-967a76606015" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_855bc3de-bc17-4308-bddd-f609dd3bade6" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_b2101ef0-4386-42af-8ea2-967a76606015" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e674be9b-5584-447c-baea-e611fc38deeb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_b2101ef0-4386-42af-8ea2-967a76606015" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e674be9b-5584-447c-baea-e611fc38deeb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e674be9b-5584-447c-baea-e611fc38deeb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e674be9b-5584-447c-baea-e611fc38deeb" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e674be9b-5584-447c-baea-e611fc38deeb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_6125dcfd-ed69-4afc-8a39-2ac7f79646ec" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e674be9b-5584-447c-baea-e611fc38deeb" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_6125dcfd-ed69-4afc-8a39-2ac7f79646ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_cd9877f8-49af-4ad9-930f-508cd17d5806" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ComputerSoftwareIntangibleAssetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_6125dcfd-ed69-4afc-8a39-2ac7f79646ec" xlink:to="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_cd9877f8-49af-4ad9-930f-508cd17d5806" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_968b72bd-9471-4dac-a764-f3a4cfc49e20" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_6125dcfd-ed69-4afc-8a39-2ac7f79646ec" xlink:to="loc_us-gaap_CustomerRelationshipsMember_968b72bd-9471-4dac-a764-f3a4cfc49e20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksMember_409fa0dd-7e7f-4d4b-babf-aab3c6db5b4f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TrademarksMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_6125dcfd-ed69-4afc-8a39-2ac7f79646ec" xlink:to="loc_us-gaap_TrademarksMember_409fa0dd-7e7f-4d4b-babf-aab3c6db5b4f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncompeteAgreementsMember_edf2d0ec-4327-4237-add2-72ae88f5a0ca" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NoncompeteAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_6125dcfd-ed69-4afc-8a39-2ac7f79646ec" xlink:to="loc_us-gaap_NoncompeteAgreementsMember_edf2d0ec-4327-4237-add2-72ae88f5a0ca" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_3dc9495c-fd46-43f9-ab54-4281f398cdb4" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_b2101ef0-4386-42af-8ea2-967a76606015" xlink:to="loc_srt_RangeAxis_3dc9495c-fd46-43f9-ab54-4281f398cdb4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_3dc9495c-fd46-43f9-ab54-4281f398cdb4_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_3dc9495c-fd46-43f9-ab54-4281f398cdb4" xlink:to="loc_srt_RangeMember_3dc9495c-fd46-43f9-ab54-4281f398cdb4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_82904293-cd5a-469d-a12e-d74a82133cef" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_3dc9495c-fd46-43f9-ab54-4281f398cdb4" xlink:to="loc_srt_RangeMember_82904293-cd5a-469d-a12e-d74a82133cef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_12d35170-0517-4a18-b0d8-bb426d38a461" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_82904293-cd5a-469d-a12e-d74a82133cef" xlink:to="loc_srt_MinimumMember_12d35170-0517-4a18-b0d8-bb426d38a461" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_39c39667-20a3-4b6b-8661-eea7d5fab4cf" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_82904293-cd5a-469d-a12e-d74a82133cef" xlink:to="loc_srt_MaximumMember_39c39667-20a3-4b6b-8661-eea7d5fab4cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_1360c0db-afa8-4a19-b510-d54dd61fa216" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwillAbstract_41b478df-8a2d-4993-a635-40b211a2b8b8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwillAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_1360c0db-afa8-4a19-b510-d54dd61fa216" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwillAbstract_41b478df-8a2d-4993-a635-40b211a2b8b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_19251079-8e88-4913-b04f-ed3e523a4436" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwillAbstract_41b478df-8a2d-4993-a635-40b211a2b8b8" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_19251079-8e88-4913-b04f-ed3e523a4436" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable_c4d8f9fb-92f2-466b-a69b-ad291c96b373" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_1360c0db-afa8-4a19-b510-d54dd61fa216" xlink:to="loc_us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable_c4d8f9fb-92f2-466b-a69b-ad291c96b373" xlink:type="arc" order="2" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_87412b97-f16a-49e5-8c02-36ef0e4f89ae" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable_c4d8f9fb-92f2-466b-a69b-ad291c96b373" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_87412b97-f16a-49e5-8c02-36ef0e4f89ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_87412b97-f16a-49e5-8c02-36ef0e4f89ae_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_87412b97-f16a-49e5-8c02-36ef0e4f89ae" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_87412b97-f16a-49e5-8c02-36ef0e4f89ae_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_ff5c9b87-2ddf-46bc-bf73-ce23d8b4986e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_87412b97-f16a-49e5-8c02-36ef0e4f89ae" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_ff5c9b87-2ddf-46bc-bf73-ce23d8b4986e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InProcessResearchAndDevelopmentMember_8effe76e-ebd3-445e-882c-170053b0991e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InProcessResearchAndDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_ff5c9b87-2ddf-46bc-bf73-ce23d8b4986e" xlink:to="loc_us-gaap_InProcessResearchAndDevelopmentMember_8effe76e-ebd3-445e-882c-170053b0991e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/InvestmentsNarrativeDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#InvestmentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/InvestmentsNarrativeDetails" xlink:type="extended" id="i14280724ee054b2b90e94a07fc06ee15_InvestmentsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_a71122ab-792b-4568-a06c-377a8e422fba" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_PaymentsToAcquireCostMethodInvestments_55446b6a-4c03-4df7-bae6-8275cccb9333" xlink:href="bsy-20220331.xsd#bsy_PaymentsToAcquireCostMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_a71122ab-792b-4568-a06c-377a8e422fba" xlink:to="loc_bsy_PaymentsToAcquireCostMethodInvestments_55446b6a-4c03-4df7-bae6-8275cccb9333" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_9037a024-7d30-476d-8f5f-a4288e6fef3c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_a71122ab-792b-4568-a06c-377a8e422fba" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_9037a024-7d30-476d-8f5f-a4288e6fef3c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_eb5177dc-8c45-4bf8-8a9b-43d1f943d6a7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_a71122ab-792b-4568-a06c-377a8e422fba" xlink:to="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_eb5177dc-8c45-4bf8-8a9b-43d1f943d6a7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_5e9958b5-91f0-4daf-ade6-e23035cc89e9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_a71122ab-792b-4568-a06c-377a8e422fba" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_5e9958b5-91f0-4daf-ade6-e23035cc89e9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_792b28ac-a09e-47ff-8a1e-bf036be285b2" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_5e9958b5-91f0-4daf-ade6-e23035cc89e9" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_792b28ac-a09e-47ff-8a1e-bf036be285b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_792b28ac-a09e-47ff-8a1e-bf036be285b2_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_792b28ac-a09e-47ff-8a1e-bf036be285b2" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_792b28ac-a09e-47ff-8a1e-bf036be285b2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_6d270c9b-dc3c-445b-b33c-14b7eb837e75" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_792b28ac-a09e-47ff-8a1e-bf036be285b2" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_6d270c9b-dc3c-445b-b33c-14b7eb837e75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DigitalConstructionWorksIncMember_66722576-734f-4eb6-8250-b2ab771fd9ee" xlink:href="bsy-20220331.xsd#bsy_DigitalConstructionWorksIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_6d270c9b-dc3c-445b-b33c-14b7eb837e75" xlink:to="loc_bsy_DigitalConstructionWorksIncMember_66722576-734f-4eb6-8250-b2ab771fd9ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_cdf0b566-b134-485d-9b5b-2fc25f388d02" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_5e9958b5-91f0-4daf-ade6-e23035cc89e9" xlink:to="loc_dei_LegalEntityAxis_cdf0b566-b134-485d-9b5b-2fc25f388d02" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_cdf0b566-b134-485d-9b5b-2fc25f388d02_default" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_cdf0b566-b134-485d-9b5b-2fc25f388d02" xlink:to="loc_dei_EntityDomain_cdf0b566-b134-485d-9b5b-2fc25f388d02_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_73620ffc-9ee1-4ad5-91ac-e6b7c3074399" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_cdf0b566-b134-485d-9b5b-2fc25f388d02" xlink:to="loc_dei_EntityDomain_73620ffc-9ee1-4ad5-91ac-e6b7c3074399" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TopconMember_50778352-708e-47f7-b0dd-b8b71390c769" xlink:href="bsy-20220331.xsd#bsy_TopconMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_73620ffc-9ee1-4ad5-91ac-e6b7c3074399" xlink:to="loc_bsy_TopconMember_50778352-708e-47f7-b0dd-b8b71390c769" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_f42be416-7dd6-4ad8-80f6-88c8d8e39fb8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_5e9958b5-91f0-4daf-ade6-e23035cc89e9" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_f42be416-7dd6-4ad8-80f6-88c8d8e39fb8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_f42be416-7dd6-4ad8-80f6-88c8d8e39fb8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_f42be416-7dd6-4ad8-80f6-88c8d8e39fb8" xlink:to="loc_us-gaap_RelatedPartyDomain_f42be416-7dd6-4ad8-80f6-88c8d8e39fb8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_f4049154-11e7-42c0-a9bc-a5d2927a8fcd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_f42be416-7dd6-4ad8-80f6-88c8d8e39fb8" xlink:to="loc_us-gaap_RelatedPartyDomain_f4049154-11e7-42c0-a9bc-a5d2927a8fcd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvesteeMember_19e8f0b3-9995-4d0e-95eb-7c77d4709d0d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityMethodInvesteeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_f4049154-11e7-42c0-a9bc-a5d2927a8fcd" xlink:to="loc_us-gaap_EquityMethodInvesteeMember_19e8f0b3-9995-4d0e-95eb-7c77d4709d0d" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/LeasesNarrativeDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#LeasesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/LeasesNarrativeDetails" xlink:type="extended" id="i503899e2a5d849378af13037daf03db3_LeasesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_685d9560-dead-418d-b47b-5471428636b2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_0438ddce-8cdd-4313-99f5-0b84761c9133" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseRemainingLeaseTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_685d9560-dead-418d-b47b-5471428636b2" xlink:to="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_0438ddce-8cdd-4313-99f5-0b84761c9133" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseRenewalTerm_7b532a6c-b66c-44e2-9f39-5c9396b6c7a1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseRenewalTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_685d9560-dead-418d-b47b-5471428636b2" xlink:to="loc_us-gaap_LesseeOperatingLeaseRenewalTerm_7b532a6c-b66c-44e2-9f39-5c9396b6c7a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_LesseeOperatingLeaseTerminationPeriod_977a7328-0bfc-47ff-86ad-d53e42a704a9" xlink:href="bsy-20220331.xsd#bsy_LesseeOperatingLeaseTerminationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_685d9560-dead-418d-b47b-5471428636b2" xlink:to="loc_bsy_LesseeOperatingLeaseTerminationPeriod_977a7328-0bfc-47ff-86ad-d53e42a704a9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_a3302829-6486-43ba-afca-21306e0512e7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_685d9560-dead-418d-b47b-5471428636b2" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_a3302829-6486-43ba-afca-21306e0512e7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_4455ed0d-5f51-4c4a-87a8-edd7898248b6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_685d9560-dead-418d-b47b-5471428636b2" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_4455ed0d-5f51-4c4a-87a8-edd7898248b6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_LesseeOperatingLeaseLeaseNotYetCommencedLiabilityLeasePayments_490fd11f-4972-4d4c-9bb3-ed4b73372fa0" xlink:href="bsy-20220331.xsd#bsy_LesseeOperatingLeaseLeaseNotYetCommencedLiabilityLeasePayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_685d9560-dead-418d-b47b-5471428636b2" xlink:to="loc_bsy_LesseeOperatingLeaseLeaseNotYetCommencedLiabilityLeasePayments_490fd11f-4972-4d4c-9bb3-ed4b73372fa0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_14c55c23-458b-4beb-9bb2-57b01b9624c9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_685d9560-dead-418d-b47b-5471428636b2" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_14c55c23-458b-4beb-9bb2-57b01b9624c9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_56f98f87-0cd0-447d-8960-84379549920f" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_14c55c23-458b-4beb-9bb2-57b01b9624c9" xlink:to="loc_srt_RangeAxis_56f98f87-0cd0-447d-8960-84379549920f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_56f98f87-0cd0-447d-8960-84379549920f_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_56f98f87-0cd0-447d-8960-84379549920f" xlink:to="loc_srt_RangeMember_56f98f87-0cd0-447d-8960-84379549920f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_b60ddf1a-58d0-494e-90d6-22cc12442ccc" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_56f98f87-0cd0-447d-8960-84379549920f" xlink:to="loc_srt_RangeMember_b60ddf1a-58d0-494e-90d6-22cc12442ccc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_b7e7dac4-1dfc-4ebd-806c-c8d4ae75e634" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_b60ddf1a-58d0-494e-90d6-22cc12442ccc" xlink:to="loc_srt_MinimumMember_b7e7dac4-1dfc-4ebd-806c-c8d4ae75e634" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_90bec311-44c9-4b1f-82e5-d23a1cef758e" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_b60ddf1a-58d0-494e-90d6-22cc12442ccc" xlink:to="loc_srt_MaximumMember_90bec311-44c9-4b1f-82e5-d23a1cef758e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/LeasesOtherInformationDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#LeasesOtherInformationDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/LeasesOtherInformationDetails" xlink:type="extended" id="if1f3025c3b8a49bda6006a193caebd21_LeasesOtherInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_958eb0b2-f5dc-4b7d-bdec-a77d399db125" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_CashFlowLesseeAbstract_aa18a28e-af46-4f69-9ef1-a995a02bcb21" xlink:href="bsy-20220331.xsd#bsy_CashFlowLesseeAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_958eb0b2-f5dc-4b7d-bdec-a77d399db125" xlink:to="loc_bsy_CashFlowLesseeAbstract_aa18a28e-af46-4f69-9ef1-a995a02bcb21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeasePayments_ceac131e-b013-4a1f-b63c-b0bc8c23a7af" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeasePayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_CashFlowLesseeAbstract_aa18a28e-af46-4f69-9ef1-a995a02bcb21" xlink:to="loc_us-gaap_OperatingLeasePayments_ceac131e-b013-4a1f-b63c-b0bc8c23a7af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_e6a15369-f76a-40cc-b7bc-e4eb264ad4cc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_CashFlowLesseeAbstract_aa18a28e-af46-4f69-9ef1-a995a02bcb21" xlink:to="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_e6a15369-f76a-40cc-b7bc-e4eb264ad4cc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCapitalLeaseObligation_21048c03-00cf-4641-9263-66bab8b844c6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCapitalLeaseObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_958eb0b2-f5dc-4b7d-bdec-a77d399db125" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCapitalLeaseObligation_21048c03-00cf-4641-9263-66bab8b844c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_837ae6f2-7fc6-4003-88bb-1801cde24541" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_958eb0b2-f5dc-4b7d-bdec-a77d399db125" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_837ae6f2-7fc6-4003-88bb-1801cde24541" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_b907b635-3d56-49e1-869b-edc4683089fb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_837ae6f2-7fc6-4003-88bb-1801cde24541" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_b907b635-3d56-49e1-869b-edc4683089fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_b907b635-3d56-49e1-869b-edc4683089fb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_b907b635-3d56-49e1-869b-edc4683089fb" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_b907b635-3d56-49e1-869b-edc4683089fb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_725db50a-1889-4a38-8441-fd77d8c210c5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_b907b635-3d56-49e1-869b-edc4683089fb" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_725db50a-1889-4a38-8441-fd77d8c210c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember_fd72726d-e70d-4fab-b4c5-fc7e5a421504" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_725db50a-1889-4a38-8441-fd77d8c210c5" xlink:to="loc_us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember_fd72726d-e70d-4fab-b4c5-fc7e5a421504" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/LongTermDebtScheduleofLongTermDebtDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#LongTermDebtScheduleofLongTermDebtDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/LongTermDebtScheduleofLongTermDebtDetails" xlink:type="extended" id="ia434d764379f488ca3152703e7fb723a_LongTermDebtScheduleofLongTermDebtDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_ff64e899-65c9-48d3-bc64-f42b6db92773" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_e4f352c9-9233-4c41-940d-0730a71a4a53" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ff64e899-65c9-48d3-bc64-f42b6db92773" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_e4f352c9-9233-4c41-940d-0730a71a4a53" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscount_30f8955e-02a0-48aa-a766-6505390700c5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentUnamortizedDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ff64e899-65c9-48d3-bc64-f42b6db92773" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscount_30f8955e-02a0-48aa-a766-6505390700c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_4bacf01d-6ec1-4889-9391-2e8f17416c74" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ff64e899-65c9-48d3-bc64-f42b6db92773" xlink:to="loc_us-gaap_LongTermDebt_4bacf01d-6ec1-4889-9391-2e8f17416c74" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_ed66d4eb-e636-4438-9537-13b3d3d4cd8a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ff64e899-65c9-48d3-bc64-f42b6db92773" xlink:to="loc_us-gaap_LongTermDebtCurrent_ed66d4eb-e636-4438-9537-13b3d3d4cd8a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_f3c7c384-2a40-4294-9282-d7d004400dd5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ff64e899-65c9-48d3-bc64-f42b6db92773" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_f3c7c384-2a40-4294-9282-d7d004400dd5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_f8ccbf33-03cb-4323-8fd6-edf009caf2cc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ff64e899-65c9-48d3-bc64-f42b6db92773" xlink:to="loc_us-gaap_DebtInstrumentTable_f8ccbf33-03cb-4323-8fd6-edf009caf2cc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_d7543e7e-2be8-49dd-b9e4-36f10ae05181" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f8ccbf33-03cb-4323-8fd6-edf009caf2cc" xlink:to="loc_us-gaap_CreditFacilityAxis_d7543e7e-2be8-49dd-b9e4-36f10ae05181" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_d7543e7e-2be8-49dd-b9e4-36f10ae05181_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_d7543e7e-2be8-49dd-b9e4-36f10ae05181" xlink:to="loc_us-gaap_CreditFacilityDomain_d7543e7e-2be8-49dd-b9e4-36f10ae05181_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_48afc8c9-9016-447e-8eb0-0f26e0b8d9fd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_d7543e7e-2be8-49dd-b9e4-36f10ae05181" xlink:to="loc_us-gaap_CreditFacilityDomain_48afc8c9-9016-447e-8eb0-0f26e0b8d9fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_62ed82fe-f53b-475d-94fa-821d8bd955af" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_48afc8c9-9016-447e-8eb0-0f26e0b8d9fd" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_62ed82fe-f53b-475d-94fa-821d8bd955af" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_0eec0b7a-84d5-4c95-a8c6-ac3bd5fd9b9d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_48afc8c9-9016-447e-8eb0-0f26e0b8d9fd" xlink:to="loc_us-gaap_SecuredDebtMember_0eec0b7a-84d5-4c95-a8c6-ac3bd5fd9b9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_512f587c-0f84-43cc-890b-f3497c633570" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f8ccbf33-03cb-4323-8fd6-edf009caf2cc" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_512f587c-0f84-43cc-890b-f3497c633570" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_512f587c-0f84-43cc-890b-f3497c633570_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_512f587c-0f84-43cc-890b-f3497c633570" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_512f587c-0f84-43cc-890b-f3497c633570_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2cdbda3e-e936-43c6-9443-05d071b9bbff" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_512f587c-0f84-43cc-890b-f3497c633570" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2cdbda3e-e936-43c6-9443-05d071b9bbff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_e01fcdd7-ab41-4586-bf12-b819c04e31df" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_2cdbda3e-e936-43c6-9443-05d071b9bbff" xlink:to="loc_us-gaap_LineOfCreditMember_e01fcdd7-ab41-4586-bf12-b819c04e31df" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_af813642-b25d-468e-844d-24a078d0b157" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_2cdbda3e-e936-43c6-9443-05d071b9bbff" xlink:to="loc_us-gaap_ConvertibleDebtMember_af813642-b25d-468e-844d-24a078d0b157" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_295d3b2d-9a9b-4bda-8f22-47ed50ec076f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f8ccbf33-03cb-4323-8fd6-edf009caf2cc" xlink:to="loc_us-gaap_DebtInstrumentAxis_295d3b2d-9a9b-4bda-8f22-47ed50ec076f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_295d3b2d-9a9b-4bda-8f22-47ed50ec076f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_295d3b2d-9a9b-4bda-8f22-47ed50ec076f" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_295d3b2d-9a9b-4bda-8f22-47ed50ec076f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_220de3ff-0e69-4943-b685-37393784420b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_295d3b2d-9a9b-4bda-8f22-47ed50ec076f" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_220de3ff-0e69-4943-b685-37393784420b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_A2021TermLoanMember_f75da26d-fa7d-4652-824c-ebed590d6fb7" xlink:href="bsy-20220331.xsd#bsy_A2021TermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_220de3ff-0e69-4943-b685-37393784420b" xlink:to="loc_bsy_A2021TermLoanMember_f75da26d-fa7d-4652-824c-ebed590d6fb7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TwoThousandTwentySixNotesMember_1a793eb4-999b-43fa-aa21-85981edf766b" xlink:href="bsy-20220331.xsd#bsy_TwoThousandTwentySixNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_220de3ff-0e69-4943-b685-37393784420b" xlink:to="loc_bsy_TwoThousandTwentySixNotesMember_1a793eb4-999b-43fa-aa21-85981edf766b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TwoThousandTwentySevenNotesMember_dcbe7f88-c479-47de-99c8-b4ec3e992b98" xlink:href="bsy-20220331.xsd#bsy_TwoThousandTwentySevenNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_220de3ff-0e69-4943-b685-37393784420b" xlink:to="loc_bsy_TwoThousandTwentySevenNotesMember_dcbe7f88-c479-47de-99c8-b4ec3e992b98" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/LongTermDebtBankCreditFacilityDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#LongTermDebtBankCreditFacilityDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/LongTermDebtBankCreditFacilityDetails" xlink:type="extended" id="i626a7f4884be4470befad73bc0c79a23_LongTermDebtBankCreditFacilityDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_38e7c314-a7a0-4d94-8c77-829900600552" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_932c5925-5a61-4ed2-9928-4b38da18ce8a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38e7c314-a7a0-4d94-8c77-829900600552" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_932c5925-5a61-4ed2-9928-4b38da18ce8a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_71cc1a33-b905-4a7f-8b62-6d2727d58437" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38e7c314-a7a0-4d94-8c77-829900600552" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_71cc1a33-b905-4a7f-8b62-6d2727d58437" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_RepaymentsOfSecuredDebtPerQuarter_0d44d62a-2e32-43b0-88c6-ae0ed9256585" xlink:href="bsy-20220331.xsd#bsy_RepaymentsOfSecuredDebtPerQuarter"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38e7c314-a7a0-4d94-8c77-829900600552" xlink:to="loc_bsy_RepaymentsOfSecuredDebtPerQuarter_0d44d62a-2e32-43b0-88c6-ae0ed9256585" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_133b4b17-3ae3-4560-9ed5-09d3cea2b768" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38e7c314-a7a0-4d94-8c77-829900600552" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_133b4b17-3ae3-4560-9ed5-09d3cea2b768" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_LineOfCreditFacilityAccordionFeatureIncreaseLimit_245ad69d-e56a-4a59-bcc0-45ea2d53fdc4" xlink:href="bsy-20220331.xsd#bsy_LineOfCreditFacilityAccordionFeatureIncreaseLimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38e7c314-a7a0-4d94-8c77-829900600552" xlink:to="loc_bsy_LineOfCreditFacilityAccordionFeatureIncreaseLimit_245ad69d-e56a-4a59-bcc0-45ea2d53fdc4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_8bd491c5-35c4-42b2-9a20-60223511fef7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38e7c314-a7a0-4d94-8c77-829900600552" xlink:to="loc_us-gaap_LongTermDebt_8bd491c5-35c4-42b2-9a20-60223511fef7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_0f0cb2b3-1768-45ab-bda8-9d1b36206ac2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38e7c314-a7a0-4d94-8c77-829900600552" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_0f0cb2b3-1768-45ab-bda8-9d1b36206ac2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_LineOfCreditFacilityBorrowingsGuaranteedThroughStockOfForeignSubsidiariesPercentage_06190a5c-03e2-44d3-a70a-9075ecfc61e7" xlink:href="bsy-20220331.xsd#bsy_LineOfCreditFacilityBorrowingsGuaranteedThroughStockOfForeignSubsidiariesPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38e7c314-a7a0-4d94-8c77-829900600552" xlink:to="loc_bsy_LineOfCreditFacilityBorrowingsGuaranteedThroughStockOfForeignSubsidiariesPercentage_06190a5c-03e2-44d3-a70a-9075ecfc61e7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_d66ecad0-d1e9-44f7-a5bc-30b185330881" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38e7c314-a7a0-4d94-8c77-829900600552" xlink:to="loc_us-gaap_DebtInstrumentTable_d66ecad0-d1e9-44f7-a5bc-30b185330881" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_bcbbee4a-3b01-4453-8507-1444ccd3c329" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_d66ecad0-d1e9-44f7-a5bc-30b185330881" xlink:to="loc_us-gaap_CreditFacilityAxis_bcbbee4a-3b01-4453-8507-1444ccd3c329" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_bcbbee4a-3b01-4453-8507-1444ccd3c329_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_bcbbee4a-3b01-4453-8507-1444ccd3c329" xlink:to="loc_us-gaap_CreditFacilityDomain_bcbbee4a-3b01-4453-8507-1444ccd3c329_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_fc5a79a0-a0ba-4933-8d23-62705641e9a5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_bcbbee4a-3b01-4453-8507-1444ccd3c329" xlink:to="loc_us-gaap_CreditFacilityDomain_fc5a79a0-a0ba-4933-8d23-62705641e9a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_e081a963-acc2-4568-8cbf-e06ea8af2114" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_fc5a79a0-a0ba-4933-8d23-62705641e9a5" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_e081a963-acc2-4568-8cbf-e06ea8af2114" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_7f795603-0b2d-47a8-bd97-5b22596bbd17" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_fc5a79a0-a0ba-4933-8d23-62705641e9a5" xlink:to="loc_us-gaap_SecuredDebtMember_7f795603-0b2d-47a8-bd97-5b22596bbd17" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_54671d25-85e1-4478-93bd-bcb13840b6ff" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_fc5a79a0-a0ba-4933-8d23-62705641e9a5" xlink:to="loc_us-gaap_LetterOfCreditMember_54671d25-85e1-4478-93bd-bcb13840b6ff" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BridgeLoanMember_ae752112-21e8-4695-8ea0-54a2096ab0b8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BridgeLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_fc5a79a0-a0ba-4933-8d23-62705641e9a5" xlink:to="loc_us-gaap_BridgeLoanMember_ae752112-21e8-4695-8ea0-54a2096ab0b8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_LettersOfCreditAndSuretyBondsMember_5425817e-d790-4643-9ebe-39efc899eab8" xlink:href="bsy-20220331.xsd#bsy_LettersOfCreditAndSuretyBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_fc5a79a0-a0ba-4933-8d23-62705641e9a5" xlink:to="loc_bsy_LettersOfCreditAndSuretyBondsMember_5425817e-d790-4643-9ebe-39efc899eab8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_b4f15240-3353-476f-87e3-b853362ecb2a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_d66ecad0-d1e9-44f7-a5bc-30b185330881" xlink:to="loc_us-gaap_DebtInstrumentAxis_b4f15240-3353-476f-87e3-b853362ecb2a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_b4f15240-3353-476f-87e3-b853362ecb2a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_b4f15240-3353-476f-87e3-b853362ecb2a" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_b4f15240-3353-476f-87e3-b853362ecb2a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_be81b566-1590-4ba9-8338-4d97178f427f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_b4f15240-3353-476f-87e3-b853362ecb2a" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_be81b566-1590-4ba9-8338-4d97178f427f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_NewCreditFacilityMember_3950a84d-cdad-4d6b-a1bc-44b956bfa8a9" xlink:href="bsy-20220331.xsd#bsy_NewCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_be81b566-1590-4ba9-8338-4d97178f427f" xlink:to="loc_bsy_NewCreditFacilityMember_3950a84d-cdad-4d6b-a1bc-44b956bfa8a9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_A2021TermLoanMember_7593e619-302d-4672-9069-b97a9484bf18" xlink:href="bsy-20220331.xsd#bsy_A2021TermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_be81b566-1590-4ba9-8338-4d97178f427f" xlink:to="loc_bsy_A2021TermLoanMember_7593e619-302d-4672-9069-b97a9484bf18" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_CreditFacilityMember_014dcd75-61f3-4ad1-b120-ee99383617dc" xlink:href="bsy-20220331.xsd#bsy_CreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_be81b566-1590-4ba9-8338-4d97178f427f" xlink:to="loc_bsy_CreditFacilityMember_014dcd75-61f3-4ad1-b120-ee99383617dc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_a1fad337-6f41-4e83-8c75-069955b2954c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_d66ecad0-d1e9-44f7-a5bc-30b185330881" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_a1fad337-6f41-4e83-8c75-069955b2954c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_a1fad337-6f41-4e83-8c75-069955b2954c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_a1fad337-6f41-4e83-8c75-069955b2954c" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_a1fad337-6f41-4e83-8c75-069955b2954c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_968aa234-20b0-467a-a5f5-061f0aa30eb7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_a1fad337-6f41-4e83-8c75-069955b2954c" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_968aa234-20b0-467a-a5f5-061f0aa30eb7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_042ad53b-5d4a-428c-a3f0-e01edf1cce6c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_968aa234-20b0-467a-a5f5-061f0aa30eb7" xlink:to="loc_us-gaap_LineOfCreditMember_042ad53b-5d4a-428c-a3f0-e01edf1cce6c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_dbab835c-d0ca-41f2-8730-6d7ed7d55ccf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_d66ecad0-d1e9-44f7-a5bc-30b185330881" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_dbab835c-d0ca-41f2-8730-6d7ed7d55ccf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_dbab835c-d0ca-41f2-8730-6d7ed7d55ccf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_dbab835c-d0ca-41f2-8730-6d7ed7d55ccf" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_dbab835c-d0ca-41f2-8730-6d7ed7d55ccf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_87e75dbc-dce2-4491-9777-4ad60d782103" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_dbab835c-d0ca-41f2-8730-6d7ed7d55ccf" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_87e75dbc-dce2-4491-9777-4ad60d782103" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_7dbe621a-fbf2-4467-baf8-83ed16a0d98f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_87e75dbc-dce2-4491-9777-4ad60d782103" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_7dbe621a-fbf2-4467-baf8-83ed16a0d98f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_04537356-d6e8-4531-a71c-fd986199d41a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_87e75dbc-dce2-4491-9777-4ad60d782103" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_04537356-d6e8-4531-a71c-fd986199d41a" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/LongTermDebt2026ConvertibleSeniorNotesDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#LongTermDebt2026ConvertibleSeniorNotesDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/LongTermDebt2026ConvertibleSeniorNotesDetails" xlink:type="extended" id="i75892dc42a594414ac3ea0234b9ca1cb_LongTermDebt2026ConvertibleSeniorNotesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_3df89625-a869-4813-bdda-fd6430f6f96a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_3df89625-a869-4813-bdda-fd6430f6f96a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_d868dc64-baf6-400e-80e8-1bb64af09f87" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_d868dc64-baf6-400e-80e8-1bb64af09f87" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts_a3298382-7aa2-49d7-b93a-48f274e7d61c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsOfDebtIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_us-gaap_PaymentsOfDebtIssuanceCosts_a3298382-7aa2-49d7-b93a-48f274e7d61c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfStockIssuanceCosts_4e403901-184a-4bae-bf5a-494ab73d97d8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsOfStockIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_us-gaap_PaymentsOfStockIssuanceCosts_4e403901-184a-4bae-bf5a-494ab73d97d8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLinesOfCredit_6896c3e4-3d70-4f23-9580-4ef36a7bd9c7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RepaymentsOfLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_us-gaap_RepaymentsOfLinesOfCredit_6896c3e4-3d70-4f23-9580-4ef36a7bd9c7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_90520675-c7bc-4c6f-a4a4-fcb157f74700" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_90520675-c7bc-4c6f-a4a4-fcb157f74700" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdTradingDays_92e8d49b-4e4c-40e7-8f72-11ddfe261715" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdTradingDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdTradingDays_92e8d49b-4e4c-40e7-8f72-11ddfe261715" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_fcfcd7f1-fb3f-47f1-bfb5-ff30af18194a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_fcfcd7f1-fb3f-47f1-bfb5-ff30af18194a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtInstrumentConvertibleThresholdConsecutiveBusinessDays_84a21d1e-e179-43a6-ad4d-b52020d150eb" xlink:href="bsy-20220331.xsd#bsy_DebtInstrumentConvertibleThresholdConsecutiveBusinessDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_bsy_DebtInstrumentConvertibleThresholdConsecutiveBusinessDays_84a21d1e-e179-43a6-ad4d-b52020d150eb" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtInstrumentConvertibleThresholdConsecutiveTradingDaysAfterThresholdConsecutiveBusinessDays_0b024d25-1e89-4c74-8156-720f12282f78" xlink:href="bsy-20220331.xsd#bsy_DebtInstrumentConvertibleThresholdConsecutiveTradingDaysAfterThresholdConsecutiveBusinessDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_bsy_DebtInstrumentConvertibleThresholdConsecutiveTradingDaysAfterThresholdConsecutiveBusinessDays_0b024d25-1e89-4c74-8156-720f12282f78" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_d40fd3e1-2dfb-4056-b93f-98e626375cba" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRedemptionPricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_d40fd3e1-2dfb-4056-b93f-98e626375cba" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtInstrumentConvertibleNumberOfEquityInstrumentsConversionRate_dd4f9a86-a9b2-45e8-8215-81ab5d816a16" xlink:href="bsy-20220331.xsd#bsy_DebtInstrumentConvertibleNumberOfEquityInstrumentsConversionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_bsy_DebtInstrumentConvertibleNumberOfEquityInstrumentsConversionRate_dd4f9a86-a9b2-45e8-8215-81ab5d816a16" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_7123394b-1394-4883-8c7c-c6fccc90be3f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_7123394b-1394-4883-8c7c-c6fccc90be3f" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_NumberOfTradingDaysAfterMaturityDateDebtRedeemable_9af1169e-c024-4ab8-b571-eacbae802561" xlink:href="bsy-20220331.xsd#bsy_NumberOfTradingDaysAfterMaturityDateDebtRedeemable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_bsy_NumberOfTradingDaysAfterMaturityDateDebtRedeemable_9af1169e-c024-4ab8-b571-eacbae802561" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtInstrumentConvertibleSharePriceThresholdAdjustmentToConversionRate_5b6c555b-2962-48fa-902a-947de27ce8c9" xlink:href="bsy-20220331.xsd#bsy_DebtInstrumentConvertibleSharePriceThresholdAdjustmentToConversionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_bsy_DebtInstrumentConvertibleSharePriceThresholdAdjustmentToConversionRate_5b6c555b-2962-48fa-902a-947de27ce8c9" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_93abb16c-2446-4528-81e8-03acec4782ad" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_93abb16c-2446-4528-81e8-03acec4782ad" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_63155b57-3b43-4c01-93a8-c5de18296667" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fe90e48d-27b4-4704-9061-3218c8082ec4" xlink:to="loc_us-gaap_DebtInstrumentTable_63155b57-3b43-4c01-93a8-c5de18296667" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_10d6fcb3-4f67-48ba-85b5-f93f797c77e9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_63155b57-3b43-4c01-93a8-c5de18296667" xlink:to="loc_us-gaap_DebtInstrumentAxis_10d6fcb3-4f67-48ba-85b5-f93f797c77e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_10d6fcb3-4f67-48ba-85b5-f93f797c77e9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_10d6fcb3-4f67-48ba-85b5-f93f797c77e9" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_10d6fcb3-4f67-48ba-85b5-f93f797c77e9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_57e08e89-d4ba-48da-880d-a2335a330623" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_10d6fcb3-4f67-48ba-85b5-f93f797c77e9" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_57e08e89-d4ba-48da-880d-a2335a330623" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TwoThousandTwentySixNotesMember_19da77bf-5368-4d58-947f-002ac0a8641d" xlink:href="bsy-20220331.xsd#bsy_TwoThousandTwentySixNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_57e08e89-d4ba-48da-880d-a2335a330623" xlink:to="loc_bsy_TwoThousandTwentySixNotesMember_19da77bf-5368-4d58-947f-002ac0a8641d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_bf0a32f6-3894-4472-be16-f8edcb3e5229" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_63155b57-3b43-4c01-93a8-c5de18296667" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_bf0a32f6-3894-4472-be16-f8edcb3e5229" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_bf0a32f6-3894-4472-be16-f8edcb3e5229_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_bf0a32f6-3894-4472-be16-f8edcb3e5229" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_bf0a32f6-3894-4472-be16-f8edcb3e5229_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_57647868-7bcc-4266-8b48-d99288eabbb2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_bf0a32f6-3894-4472-be16-f8edcb3e5229" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_57647868-7bcc-4266-8b48-d99288eabbb2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_9eb8ae20-fd8b-417d-838f-a04826f82d10" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_57647868-7bcc-4266-8b48-d99288eabbb2" xlink:to="loc_us-gaap_ConvertibleDebtMember_9eb8ae20-fd8b-417d-838f-a04826f82d10" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtInstrumentConvertibleTermsOfConversionAxis_3a6da5a8-673d-41a0-82d8-cb57ac2ce22b" xlink:href="bsy-20220331.xsd#bsy_DebtInstrumentConvertibleTermsOfConversionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_63155b57-3b43-4c01-93a8-c5de18296667" xlink:to="loc_bsy_DebtInstrumentConvertibleTermsOfConversionAxis_3a6da5a8-673d-41a0-82d8-cb57ac2ce22b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtInstrumentConvertibleTermsOfConversionDomain_3a6da5a8-673d-41a0-82d8-cb57ac2ce22b_default" xlink:href="bsy-20220331.xsd#bsy_DebtInstrumentConvertibleTermsOfConversionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_bsy_DebtInstrumentConvertibleTermsOfConversionAxis_3a6da5a8-673d-41a0-82d8-cb57ac2ce22b" xlink:to="loc_bsy_DebtInstrumentConvertibleTermsOfConversionDomain_3a6da5a8-673d-41a0-82d8-cb57ac2ce22b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtInstrumentConvertibleTermsOfConversionDomain_d9e93018-2be9-4dbd-83a6-acb32ac572b8" xlink:href="bsy-20220331.xsd#bsy_DebtInstrumentConvertibleTermsOfConversionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_bsy_DebtInstrumentConvertibleTermsOfConversionAxis_3a6da5a8-673d-41a0-82d8-cb57ac2ce22b" xlink:to="loc_bsy_DebtInstrumentConvertibleTermsOfConversionDomain_d9e93018-2be9-4dbd-83a6-acb32ac572b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtConversionTermsOneMember_5c68f470-8466-41d0-a846-298596e4cfa6" xlink:href="bsy-20220331.xsd#bsy_DebtConversionTermsOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_DebtInstrumentConvertibleTermsOfConversionDomain_d9e93018-2be9-4dbd-83a6-acb32ac572b8" xlink:to="loc_bsy_DebtConversionTermsOneMember_5c68f470-8466-41d0-a846-298596e4cfa6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtConversionTermsTwoMember_dfe94fac-9558-43b4-8da7-db991f3ee1df" xlink:href="bsy-20220331.xsd#bsy_DebtConversionTermsTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_DebtInstrumentConvertibleTermsOfConversionDomain_d9e93018-2be9-4dbd-83a6-acb32ac572b8" xlink:to="loc_bsy_DebtConversionTermsTwoMember_dfe94fac-9558-43b4-8da7-db991f3ee1df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_d5a56321-7c26-4190-8688-c419420566a3" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_63155b57-3b43-4c01-93a8-c5de18296667" xlink:to="loc_srt_RangeAxis_d5a56321-7c26-4190-8688-c419420566a3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_d5a56321-7c26-4190-8688-c419420566a3_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_d5a56321-7c26-4190-8688-c419420566a3" xlink:to="loc_srt_RangeMember_d5a56321-7c26-4190-8688-c419420566a3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_627b1e06-f9ec-4089-af2d-205fb648d281" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_d5a56321-7c26-4190-8688-c419420566a3" xlink:to="loc_srt_RangeMember_627b1e06-f9ec-4089-af2d-205fb648d281" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_ea10c864-60f4-4a68-a824-008e88835034" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_627b1e06-f9ec-4089-af2d-205fb648d281" xlink:to="loc_srt_MinimumMember_ea10c864-60f4-4a68-a824-008e88835034" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_89ef3f25-d89c-4061-aa43-404a7251e877" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_627b1e06-f9ec-4089-af2d-205fb648d281" xlink:to="loc_srt_MaximumMember_89ef3f25-d89c-4061-aa43-404a7251e877" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/LongTermDebt2026NotesCappedCallOptionsDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#LongTermDebt2026NotesCappedCallOptionsDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/LongTermDebt2026NotesCappedCallOptionsDetails" xlink:type="extended" id="ie8ee9b8ce5204a2f8fe329c18b597fd8_LongTermDebt2026NotesCappedCallOptionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_4fe7792f-463b-44d5-8a43-53b3a4369b78" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_CappedCallOptionsExpense_5e9abf62-aa01-4937-a4b9-58346efb05d4" xlink:href="bsy-20220331.xsd#bsy_CappedCallOptionsExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_4fe7792f-463b-44d5-8a43-53b3a4369b78" xlink:to="loc_bsy_CappedCallOptionsExpense_5e9abf62-aa01-4937-a4b9-58346efb05d4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OptionIndexedToIssuersEquityStrikePrice1_5b322af9-a0cd-466c-b1b1-2c1e4d4c6a1a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OptionIndexedToIssuersEquityStrikePrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_4fe7792f-463b-44d5-8a43-53b3a4369b78" xlink:to="loc_us-gaap_OptionIndexedToIssuersEquityStrikePrice1_5b322af9-a0cd-466c-b1b1-2c1e4d4c6a1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_OptionIndexedToIssuersEquityStrikePricePremiumOverSharePricePercentage_ec804353-7d89-4c6b-9573-683d4f183ab2" xlink:href="bsy-20220331.xsd#bsy_OptionIndexedToIssuersEquityStrikePricePremiumOverSharePricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_4fe7792f-463b-44d5-8a43-53b3a4369b78" xlink:to="loc_bsy_OptionIndexedToIssuersEquityStrikePricePremiumOverSharePricePercentage_ec804353-7d89-4c6b-9573-683d4f183ab2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_396a8443-222f-4b1c-b360-4027fcb89c6d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_4fe7792f-463b-44d5-8a43-53b3a4369b78" xlink:to="loc_us-gaap_DebtInstrumentTable_396a8443-222f-4b1c-b360-4027fcb89c6d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_702ea68d-58b8-415b-ba99-33dddd6ddc58" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_396a8443-222f-4b1c-b360-4027fcb89c6d" xlink:to="loc_us-gaap_DebtInstrumentAxis_702ea68d-58b8-415b-ba99-33dddd6ddc58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_702ea68d-58b8-415b-ba99-33dddd6ddc58_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_702ea68d-58b8-415b-ba99-33dddd6ddc58" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_702ea68d-58b8-415b-ba99-33dddd6ddc58_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_48f8f3cf-9029-4d8b-bc43-c62875e009e9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_702ea68d-58b8-415b-ba99-33dddd6ddc58" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_48f8f3cf-9029-4d8b-bc43-c62875e009e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TwoThousandTwentySixNotesMember_6e2a527e-0d2d-4e77-9d29-57ac8971fb3e" xlink:href="bsy-20220331.xsd#bsy_TwoThousandTwentySixNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_48f8f3cf-9029-4d8b-bc43-c62875e009e9" xlink:to="loc_bsy_TwoThousandTwentySixNotesMember_6e2a527e-0d2d-4e77-9d29-57ac8971fb3e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_6fcda286-74a6-4405-9c39-8a47cfb7c7db" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_396a8443-222f-4b1c-b360-4027fcb89c6d" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_6fcda286-74a6-4405-9c39-8a47cfb7c7db" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_6fcda286-74a6-4405-9c39-8a47cfb7c7db_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_6fcda286-74a6-4405-9c39-8a47cfb7c7db" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_6fcda286-74a6-4405-9c39-8a47cfb7c7db_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2b952e48-85f0-4896-a32a-f57797667fd7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_6fcda286-74a6-4405-9c39-8a47cfb7c7db" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2b952e48-85f0-4896-a32a-f57797667fd7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_3ac9f18c-9c17-48b4-a785-20b41b8f0f86" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_2b952e48-85f0-4896-a32a-f57797667fd7" xlink:to="loc_us-gaap_ConvertibleDebtMember_3ac9f18c-9c17-48b4-a785-20b41b8f0f86" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/LongTermDebt2027ConvertibleSeniorNotesDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#LongTermDebt2027ConvertibleSeniorNotesDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/LongTermDebt2027ConvertibleSeniorNotesDetails" xlink:type="extended" id="ie46fd7d6fcbe473e836dce7d2e446356_LongTermDebt2027ConvertibleSeniorNotesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_44ffc4e6-881e-46f6-9d73-0a11c13411ed" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_44ffc4e6-881e-46f6-9d73-0a11c13411ed" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_e3f62a1d-ca95-4a1a-b620-a7a987a7c16a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_e3f62a1d-ca95-4a1a-b620-a7a987a7c16a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts_62c75cc2-36b8-48a2-9ae9-05391120f4c9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsOfDebtIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_us-gaap_PaymentsOfDebtIssuanceCosts_62c75cc2-36b8-48a2-9ae9-05391120f4c9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfStockIssuanceCosts_d9a1d552-72d6-48a0-a584-0b92f3551aa8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsOfStockIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_us-gaap_PaymentsOfStockIssuanceCosts_d9a1d552-72d6-48a0-a584-0b92f3551aa8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLinesOfCredit_c68e195a-63ce-4a16-8188-fe8906adc04b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RepaymentsOfLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_us-gaap_RepaymentsOfLinesOfCredit_c68e195a-63ce-4a16-8188-fe8906adc04b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_d8c74911-eba9-4c70-a245-1b782430fbb5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_d8c74911-eba9-4c70-a245-1b782430fbb5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdTradingDays_47354038-a435-43e8-a8e8-d09337cf3b39" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdTradingDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdTradingDays_47354038-a435-43e8-a8e8-d09337cf3b39" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_7375ecc3-bd57-476b-897d-0b3a8a01a960" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_7375ecc3-bd57-476b-897d-0b3a8a01a960" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtInstrumentConvertibleThresholdConsecutiveBusinessDays_518a4f51-4131-497b-966b-18dda8459a94" xlink:href="bsy-20220331.xsd#bsy_DebtInstrumentConvertibleThresholdConsecutiveBusinessDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_bsy_DebtInstrumentConvertibleThresholdConsecutiveBusinessDays_518a4f51-4131-497b-966b-18dda8459a94" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtInstrumentConvertibleThresholdConsecutiveTradingDaysAfterThresholdConsecutiveBusinessDays_5885cb60-7921-41d5-bc65-567ef2469584" xlink:href="bsy-20220331.xsd#bsy_DebtInstrumentConvertibleThresholdConsecutiveTradingDaysAfterThresholdConsecutiveBusinessDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_bsy_DebtInstrumentConvertibleThresholdConsecutiveTradingDaysAfterThresholdConsecutiveBusinessDays_5885cb60-7921-41d5-bc65-567ef2469584" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_5dec4536-186e-49eb-8005-509e91d18573" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRedemptionPricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_5dec4536-186e-49eb-8005-509e91d18573" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtInstrumentConvertibleNumberOfEquityInstrumentsConversionRate_362d340b-c27a-4f06-acfc-1a9d47c7071b" xlink:href="bsy-20220331.xsd#bsy_DebtInstrumentConvertibleNumberOfEquityInstrumentsConversionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_bsy_DebtInstrumentConvertibleNumberOfEquityInstrumentsConversionRate_362d340b-c27a-4f06-acfc-1a9d47c7071b" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_77965bf7-db77-435a-918e-b1d86f5cb88f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_77965bf7-db77-435a-918e-b1d86f5cb88f" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_NumberOfTradingDaysAfterMaturityDateDebtRedeemable_9b567f59-d524-47b9-ad31-ad4ba4230765" xlink:href="bsy-20220331.xsd#bsy_NumberOfTradingDaysAfterMaturityDateDebtRedeemable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_bsy_NumberOfTradingDaysAfterMaturityDateDebtRedeemable_9b567f59-d524-47b9-ad31-ad4ba4230765" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtInstrumentConvertibleSharePriceThresholdAdjustmentToConversionRate_6c1959a5-c6f0-4d6b-9c24-933c2678c942" xlink:href="bsy-20220331.xsd#bsy_DebtInstrumentConvertibleSharePriceThresholdAdjustmentToConversionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_bsy_DebtInstrumentConvertibleSharePriceThresholdAdjustmentToConversionRate_6c1959a5-c6f0-4d6b-9c24-933c2678c942" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_0f3cc02e-9d69-4cd5-b09b-058555e44b90" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_0f3cc02e-9d69-4cd5-b09b-058555e44b90" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_a5441765-0b3e-40bc-ac6f-c979f3a199b6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cfd840c1-a7b8-4a5b-bbca-9deeb21ee087" xlink:to="loc_us-gaap_DebtInstrumentTable_a5441765-0b3e-40bc-ac6f-c979f3a199b6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_497a51d8-7d01-4b13-80c0-5f2e395cc2b5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_a5441765-0b3e-40bc-ac6f-c979f3a199b6" xlink:to="loc_us-gaap_DebtInstrumentAxis_497a51d8-7d01-4b13-80c0-5f2e395cc2b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_497a51d8-7d01-4b13-80c0-5f2e395cc2b5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_497a51d8-7d01-4b13-80c0-5f2e395cc2b5" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_497a51d8-7d01-4b13-80c0-5f2e395cc2b5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_660dfcc9-4d96-4133-876c-1ef9365ad927" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_497a51d8-7d01-4b13-80c0-5f2e395cc2b5" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_660dfcc9-4d96-4133-876c-1ef9365ad927" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TwoThousandTwentySevenNotesMember_3f1e84f8-5f3c-4afe-87c5-866e36223b18" xlink:href="bsy-20220331.xsd#bsy_TwoThousandTwentySevenNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_660dfcc9-4d96-4133-876c-1ef9365ad927" xlink:to="loc_bsy_TwoThousandTwentySevenNotesMember_3f1e84f8-5f3c-4afe-87c5-866e36223b18" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_ced5f7f4-ba9a-4680-9831-d8081e8cb06d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_a5441765-0b3e-40bc-ac6f-c979f3a199b6" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_ced5f7f4-ba9a-4680-9831-d8081e8cb06d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_ced5f7f4-ba9a-4680-9831-d8081e8cb06d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ced5f7f4-ba9a-4680-9831-d8081e8cb06d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_ced5f7f4-ba9a-4680-9831-d8081e8cb06d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_6eb469e2-3b7a-4785-b18a-7c891829d107" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ced5f7f4-ba9a-4680-9831-d8081e8cb06d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_6eb469e2-3b7a-4785-b18a-7c891829d107" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_29b1a045-7bde-4a67-8c1d-6a84366da93e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_6eb469e2-3b7a-4785-b18a-7c891829d107" xlink:to="loc_us-gaap_ConvertibleDebtMember_29b1a045-7bde-4a67-8c1d-6a84366da93e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtInstrumentConvertibleTermsOfConversionAxis_7a9d368c-2030-4113-be9e-64b056e630ee" xlink:href="bsy-20220331.xsd#bsy_DebtInstrumentConvertibleTermsOfConversionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_a5441765-0b3e-40bc-ac6f-c979f3a199b6" xlink:to="loc_bsy_DebtInstrumentConvertibleTermsOfConversionAxis_7a9d368c-2030-4113-be9e-64b056e630ee" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtInstrumentConvertibleTermsOfConversionDomain_7a9d368c-2030-4113-be9e-64b056e630ee_default" xlink:href="bsy-20220331.xsd#bsy_DebtInstrumentConvertibleTermsOfConversionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_bsy_DebtInstrumentConvertibleTermsOfConversionAxis_7a9d368c-2030-4113-be9e-64b056e630ee" xlink:to="loc_bsy_DebtInstrumentConvertibleTermsOfConversionDomain_7a9d368c-2030-4113-be9e-64b056e630ee_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtInstrumentConvertibleTermsOfConversionDomain_728efa74-2de2-4342-b309-e1d95daa7479" xlink:href="bsy-20220331.xsd#bsy_DebtInstrumentConvertibleTermsOfConversionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_bsy_DebtInstrumentConvertibleTermsOfConversionAxis_7a9d368c-2030-4113-be9e-64b056e630ee" xlink:to="loc_bsy_DebtInstrumentConvertibleTermsOfConversionDomain_728efa74-2de2-4342-b309-e1d95daa7479" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtConversionTermsOneMember_3cd7b61a-4cbf-4b8f-993a-79b070e2c052" xlink:href="bsy-20220331.xsd#bsy_DebtConversionTermsOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_DebtInstrumentConvertibleTermsOfConversionDomain_728efa74-2de2-4342-b309-e1d95daa7479" xlink:to="loc_bsy_DebtConversionTermsOneMember_3cd7b61a-4cbf-4b8f-993a-79b070e2c052" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DebtConversionTermsTwoMember_ff80aeb8-09d2-4c05-8c08-bcc4ef8543fe" xlink:href="bsy-20220331.xsd#bsy_DebtConversionTermsTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_DebtInstrumentConvertibleTermsOfConversionDomain_728efa74-2de2-4342-b309-e1d95daa7479" xlink:to="loc_bsy_DebtConversionTermsTwoMember_ff80aeb8-09d2-4c05-8c08-bcc4ef8543fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_d9ec7ad4-7935-4c8e-b2f6-93a3506d6060" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_a5441765-0b3e-40bc-ac6f-c979f3a199b6" xlink:to="loc_srt_RangeAxis_d9ec7ad4-7935-4c8e-b2f6-93a3506d6060" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_d9ec7ad4-7935-4c8e-b2f6-93a3506d6060_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_d9ec7ad4-7935-4c8e-b2f6-93a3506d6060" xlink:to="loc_srt_RangeMember_d9ec7ad4-7935-4c8e-b2f6-93a3506d6060_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_c5d58717-64a6-4323-9884-ac41ae39db74" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_d9ec7ad4-7935-4c8e-b2f6-93a3506d6060" xlink:to="loc_srt_RangeMember_c5d58717-64a6-4323-9884-ac41ae39db74" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_ea09ddc0-7978-42c5-96f2-a787027facb6" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_c5d58717-64a6-4323-9884-ac41ae39db74" xlink:to="loc_srt_MinimumMember_ea09ddc0-7978-42c5-96f2-a787027facb6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_1b61d99d-3b2b-485a-9208-17bd65c05a9e" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_c5d58717-64a6-4323-9884-ac41ae39db74" xlink:to="loc_srt_MaximumMember_1b61d99d-3b2b-485a-9208-17bd65c05a9e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/LongTermDebt2027NotesCappedCallOptionsDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#LongTermDebt2027NotesCappedCallOptionsDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/LongTermDebt2027NotesCappedCallOptionsDetails" xlink:type="extended" id="i33c5fd80822649b2ac4e442e4f6d02f9_LongTermDebt2027NotesCappedCallOptionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_f73c6788-46e8-41a5-8551-54b55b1b3ca8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_CappedCallOptionsExpense_347179c5-7b7e-40c3-a789-76e2b98f5065" xlink:href="bsy-20220331.xsd#bsy_CappedCallOptionsExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_f73c6788-46e8-41a5-8551-54b55b1b3ca8" xlink:to="loc_bsy_CappedCallOptionsExpense_347179c5-7b7e-40c3-a789-76e2b98f5065" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OptionIndexedToIssuersEquityStrikePrice1_8c054a88-ce3c-414c-9aee-cc0d47fcc7c6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OptionIndexedToIssuersEquityStrikePrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_f73c6788-46e8-41a5-8551-54b55b1b3ca8" xlink:to="loc_us-gaap_OptionIndexedToIssuersEquityStrikePrice1_8c054a88-ce3c-414c-9aee-cc0d47fcc7c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_OptionIndexedToIssuersEquityStrikePricePremiumOverSharePricePercentage_62a710c5-ae2c-49ff-a10b-d77247667cc4" xlink:href="bsy-20220331.xsd#bsy_OptionIndexedToIssuersEquityStrikePricePremiumOverSharePricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_f73c6788-46e8-41a5-8551-54b55b1b3ca8" xlink:to="loc_bsy_OptionIndexedToIssuersEquityStrikePricePremiumOverSharePricePercentage_62a710c5-ae2c-49ff-a10b-d77247667cc4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_01c0343a-7807-469b-ac35-7591f25d4494" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_f73c6788-46e8-41a5-8551-54b55b1b3ca8" xlink:to="loc_us-gaap_DebtInstrumentTable_01c0343a-7807-469b-ac35-7591f25d4494" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_47e8ae44-6e82-440c-a3bc-c76919a09c3b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_01c0343a-7807-469b-ac35-7591f25d4494" xlink:to="loc_us-gaap_DebtInstrumentAxis_47e8ae44-6e82-440c-a3bc-c76919a09c3b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_47e8ae44-6e82-440c-a3bc-c76919a09c3b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_47e8ae44-6e82-440c-a3bc-c76919a09c3b" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_47e8ae44-6e82-440c-a3bc-c76919a09c3b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_e73abb45-4181-4f90-804e-36916b6c6c00" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_47e8ae44-6e82-440c-a3bc-c76919a09c3b" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_e73abb45-4181-4f90-804e-36916b6c6c00" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TwoThousandTwentySevenNotesMember_ed9c7ed1-3ea5-4e1b-9f43-836c3f400476" xlink:href="bsy-20220331.xsd#bsy_TwoThousandTwentySevenNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_e73abb45-4181-4f90-804e-36916b6c6c00" xlink:to="loc_bsy_TwoThousandTwentySevenNotesMember_ed9c7ed1-3ea5-4e1b-9f43-836c3f400476" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_2b707bff-ccde-4413-9351-b9ec4656cb9c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_01c0343a-7807-469b-ac35-7591f25d4494" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_2b707bff-ccde-4413-9351-b9ec4656cb9c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2b707bff-ccde-4413-9351-b9ec4656cb9c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_2b707bff-ccde-4413-9351-b9ec4656cb9c" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2b707bff-ccde-4413-9351-b9ec4656cb9c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_5bf8ad1c-508c-4805-b0ad-745c4e2fa0d5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_2b707bff-ccde-4413-9351-b9ec4656cb9c" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_5bf8ad1c-508c-4805-b0ad-745c4e2fa0d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_461b7c98-8420-4348-94ca-e5291c6c472c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_5bf8ad1c-508c-4805-b0ad-745c4e2fa0d5" xlink:to="loc_us-gaap_ConvertibleDebtMember_461b7c98-8420-4348-94ca-e5291c6c472c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/LongTermDebtScheduleofInterestExpenseDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#LongTermDebtScheduleofInterestExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/LongTermDebtScheduleofInterestExpenseDetails" xlink:type="extended" id="i055e8c7340b44c33a0b594c6b717f488_LongTermDebtScheduleofInterestExpenseDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_683dd23d-474c-4f63-8431-188fb4be0c17" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebtExcludingAmortization_1ee06542-0521-4301-88e6-a5f8e330347a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestExpenseDebtExcludingAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_683dd23d-474c-4f63-8431-188fb4be0c17" xlink:to="loc_us-gaap_InterestExpenseDebtExcludingAmortization_1ee06542-0521-4301-88e6-a5f8e330347a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_InterestExpenseDerivatives_327f220b-2860-4c7f-8437-5dd18993a7d2" xlink:href="bsy-20220331.xsd#bsy_InterestExpenseDerivatives"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_683dd23d-474c-4f63-8431-188fb4be0c17" xlink:to="loc_bsy_InterestExpenseDerivatives_327f220b-2860-4c7f-8437-5dd18993a7d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_0f9187da-1eef-48c6-bddd-e2e7a23872d6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_683dd23d-474c-4f63-8431-188fb4be0c17" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_0f9187da-1eef-48c6-bddd-e2e7a23872d6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_cb36d2d9-589b-438f-8071-8bfd98c2dfe1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_683dd23d-474c-4f63-8431-188fb4be0c17" xlink:to="loc_us-gaap_InterestExpenseDebt_cb36d2d9-589b-438f-8071-8bfd98c2dfe1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_e56edbd5-56d6-4dd9-ad45-27237e0b3c84" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_683dd23d-474c-4f63-8431-188fb4be0c17" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_e56edbd5-56d6-4dd9-ad45-27237e0b3c84" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseOther_fcf34f6d-4a2a-47a8-adc8-dd6ced1fd193" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestExpenseOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_683dd23d-474c-4f63-8431-188fb4be0c17" xlink:to="loc_us-gaap_InterestExpenseOther_fcf34f6d-4a2a-47a8-adc8-dd6ced1fd193" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_d264291e-c981-4756-a316-d231363be5c6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_683dd23d-474c-4f63-8431-188fb4be0c17" xlink:to="loc_us-gaap_InterestExpense_d264291e-c981-4756-a316-d231363be5c6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtWeightedAverageInterestRateOverTime_a0cd791c-ad36-45f9-b16f-0b5576fe5d6c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtWeightedAverageInterestRateOverTime"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_683dd23d-474c-4f63-8431-188fb4be0c17" xlink:to="loc_us-gaap_LongTermDebtWeightedAverageInterestRateOverTime_a0cd791c-ad36-45f9-b16f-0b5576fe5d6c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_8d780a4c-df8b-40b3-9705-aede1da22a0e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_683dd23d-474c-4f63-8431-188fb4be0c17" xlink:to="loc_us-gaap_DebtInstrumentTable_8d780a4c-df8b-40b3-9705-aede1da22a0e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_65c36893-b233-42d3-8a5b-6d26e724c9bb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8d780a4c-df8b-40b3-9705-aede1da22a0e" xlink:to="loc_us-gaap_DebtInstrumentAxis_65c36893-b233-42d3-8a5b-6d26e724c9bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_65c36893-b233-42d3-8a5b-6d26e724c9bb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_65c36893-b233-42d3-8a5b-6d26e724c9bb" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_65c36893-b233-42d3-8a5b-6d26e724c9bb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_2737b164-129f-4d5a-9453-56920b9c28b6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_65c36893-b233-42d3-8a5b-6d26e724c9bb" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_2737b164-129f-4d5a-9453-56920b9c28b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_A2021TermLoanMember_247cdbd1-1a35-4d07-adad-df3db5bc5064" xlink:href="bsy-20220331.xsd#bsy_A2021TermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_2737b164-129f-4d5a-9453-56920b9c28b6" xlink:to="loc_bsy_A2021TermLoanMember_247cdbd1-1a35-4d07-adad-df3db5bc5064" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TwoThousandTwentySixNotesMember_3cf9e8fd-8918-4652-b253-f2e377beb69c" xlink:href="bsy-20220331.xsd#bsy_TwoThousandTwentySixNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_2737b164-129f-4d5a-9453-56920b9c28b6" xlink:to="loc_bsy_TwoThousandTwentySixNotesMember_3cf9e8fd-8918-4652-b253-f2e377beb69c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TwoThousandTwentySevenNotesMember_96c82b0e-9f4c-41b8-b477-f8bd1493ba91" xlink:href="bsy-20220331.xsd#bsy_TwoThousandTwentySevenNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_2737b164-129f-4d5a-9453-56920b9c28b6" xlink:to="loc_bsy_TwoThousandTwentySevenNotesMember_96c82b0e-9f4c-41b8-b477-f8bd1493ba91" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_CreditFacilityMember_575d5f4e-b89c-45c1-b2e1-dfbb2aa4d130" xlink:href="bsy-20220331.xsd#bsy_CreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_2737b164-129f-4d5a-9453-56920b9c28b6" xlink:to="loc_bsy_CreditFacilityMember_575d5f4e-b89c-45c1-b2e1-dfbb2aa4d130" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_4d1f1d6a-b202-4fcd-988d-3efb590e3b82" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8d780a4c-df8b-40b3-9705-aede1da22a0e" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_4d1f1d6a-b202-4fcd-988d-3efb590e3b82" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_4d1f1d6a-b202-4fcd-988d-3efb590e3b82_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_4d1f1d6a-b202-4fcd-988d-3efb590e3b82" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_4d1f1d6a-b202-4fcd-988d-3efb590e3b82_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_b803c7e0-8c74-4113-bee7-8edac5a418d1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_4d1f1d6a-b202-4fcd-988d-3efb590e3b82" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_b803c7e0-8c74-4113-bee7-8edac5a418d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_5b7980ad-7587-4daf-a0e6-72c656ac9456" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_b803c7e0-8c74-4113-bee7-8edac5a418d1" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_5b7980ad-7587-4daf-a0e6-72c656ac9456" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_d610752e-df1f-40de-9c0c-9d9cfa0cee3a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_b803c7e0-8c74-4113-bee7-8edac5a418d1" xlink:to="loc_us-gaap_SecuredDebtMember_d610752e-df1f-40de-9c0c-9d9cfa0cee3a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_b517d94b-c1a1-4fd7-8b9a-b32c3ebb735f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_b803c7e0-8c74-4113-bee7-8edac5a418d1" xlink:to="loc_us-gaap_ConvertibleDebtMember_b517d94b-c1a1-4fd7-8b9a-b32c3ebb735f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_31e32a42-9aca-46ea-8658-8ecab9e2a694" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8d780a4c-df8b-40b3-9705-aede1da22a0e" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_31e32a42-9aca-46ea-8658-8ecab9e2a694" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_31e32a42-9aca-46ea-8658-8ecab9e2a694_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_31e32a42-9aca-46ea-8658-8ecab9e2a694" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_31e32a42-9aca-46ea-8658-8ecab9e2a694_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_c2d64066-f8c2-46ef-bc47-cc2574147345" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_31e32a42-9aca-46ea-8658-8ecab9e2a694" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_c2d64066-f8c2-46ef-bc47-cc2574147345" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_76b081e3-11d6-4c6a-b5da-b092d8ec229f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_c2d64066-f8c2-46ef-bc47-cc2574147345" xlink:to="loc_us-gaap_InterestRateSwapMember_76b081e3-11d6-4c6a-b5da-b092d8ec229f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/LongTermDebtNarrativeDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#LongTermDebtNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/LongTermDebtNarrativeDetails" xlink:type="extended" id="ia67ef53f2b05445fb967568d54dc0306_LongTermDebtNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_6578fcbb-b780-4876-83bb-058a0be71ed0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_c553381f-d8bc-4313-8daa-d8fc2ead5b03" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6578fcbb-b780-4876-83bb-058a0be71ed0" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_c553381f-d8bc-4313-8daa-d8fc2ead5b03" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_794704cd-2011-4d4e-bcdf-9b5606065d07" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6578fcbb-b780-4876-83bb-058a0be71ed0" xlink:to="loc_us-gaap_DerivativeNotionalAmount_794704cd-2011-4d4e-bcdf-9b5606065d07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeNet_f58ab9e6-3749-4bdf-8386-5cdb7bd10153" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeFairValueOfDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6578fcbb-b780-4876-83bb-058a0be71ed0" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeNet_f58ab9e6-3749-4bdf-8386-5cdb7bd10153" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_c1312de5-5cbf-4447-b07b-c4543d2bfce4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6578fcbb-b780-4876-83bb-058a0be71ed0" xlink:to="loc_us-gaap_DebtInstrumentTable_c1312de5-5cbf-4447-b07b-c4543d2bfce4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_eb84e857-1c46-48b2-a799-85c3a3cbad59" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c1312de5-5cbf-4447-b07b-c4543d2bfce4" xlink:to="loc_us-gaap_DebtInstrumentAxis_eb84e857-1c46-48b2-a799-85c3a3cbad59" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_eb84e857-1c46-48b2-a799-85c3a3cbad59_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_eb84e857-1c46-48b2-a799-85c3a3cbad59" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_eb84e857-1c46-48b2-a799-85c3a3cbad59_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_30568993-cc3d-4deb-9d92-d57b1b2418f4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_eb84e857-1c46-48b2-a799-85c3a3cbad59" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_30568993-cc3d-4deb-9d92-d57b1b2418f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_CreditFacilityMember_38ff84a7-5e48-4509-8585-7d1befa76377" xlink:href="bsy-20220331.xsd#bsy_CreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_30568993-cc3d-4deb-9d92-d57b1b2418f4" xlink:to="loc_bsy_CreditFacilityMember_38ff84a7-5e48-4509-8585-7d1befa76377" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_12501953-8549-414e-ada9-94be477dee1e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c1312de5-5cbf-4447-b07b-c4543d2bfce4" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_12501953-8549-414e-ada9-94be477dee1e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_12501953-8549-414e-ada9-94be477dee1e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_12501953-8549-414e-ada9-94be477dee1e" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_12501953-8549-414e-ada9-94be477dee1e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_cd939f3c-876b-4805-8324-c15ba34c5e51" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_12501953-8549-414e-ada9-94be477dee1e" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_cd939f3c-876b-4805-8324-c15ba34c5e51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_a19e22f7-bbd9-4517-8f18-8519e2496f2d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_cd939f3c-876b-4805-8324-c15ba34c5e51" xlink:to="loc_us-gaap_LineOfCreditMember_a19e22f7-bbd9-4517-8f18-8519e2496f2d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_216f5e98-a3f3-42b3-b129-70d521bf5ce0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c1312de5-5cbf-4447-b07b-c4543d2bfce4" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_216f5e98-a3f3-42b3-b129-70d521bf5ce0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_216f5e98-a3f3-42b3-b129-70d521bf5ce0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_216f5e98-a3f3-42b3-b129-70d521bf5ce0" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_216f5e98-a3f3-42b3-b129-70d521bf5ce0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_563bf827-3125-43ec-963c-3a96c08eb7a9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_216f5e98-a3f3-42b3-b129-70d521bf5ce0" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_563bf827-3125-43ec-963c-3a96c08eb7a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_ff80c19c-5161-47e3-a07a-e853a0ed9895" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_563bf827-3125-43ec-963c-3a96c08eb7a9" xlink:to="loc_us-gaap_InterestRateSwapMember_ff80c19c-5161-47e3-a07a-e853a0ed9895" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_44aab82c-6c3c-4e04-ab79-2cb2bcb6f14a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c1312de5-5cbf-4447-b07b-c4543d2bfce4" xlink:to="loc_us-gaap_HedgingDesignationAxis_44aab82c-6c3c-4e04-ab79-2cb2bcb6f14a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_44aab82c-6c3c-4e04-ab79-2cb2bcb6f14a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_44aab82c-6c3c-4e04-ab79-2cb2bcb6f14a" xlink:to="loc_us-gaap_HedgingDesignationDomain_44aab82c-6c3c-4e04-ab79-2cb2bcb6f14a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_c149801b-b638-47ba-adf7-4f0f6f78324b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_44aab82c-6c3c-4e04-ab79-2cb2bcb6f14a" xlink:to="loc_us-gaap_HedgingDesignationDomain_c149801b-b638-47ba-adf7-4f0f6f78324b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_8c511643-ca46-45ba-84a6-115e6a9aa8e0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_c149801b-b638-47ba-adf7-4f0f6f78324b" xlink:to="loc_us-gaap_NondesignatedMember_8c511643-ca46-45ba-84a6-115e6a9aa8e0" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/ExecutiveBonusPlanNarrativeDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#ExecutiveBonusPlanNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/ExecutiveBonusPlanNarrativeDetails" xlink:type="extended" id="i05d9537cfa4245a2818db8ee5e931119_ExecutiveBonusPlanNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsLineItems_b1d0857f-816c-4c70-a6a4-bad739916f9c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DeferredCompensationArrangementWithIndividualManagementReportOperatingIncomeFundingThreshold_10bdd2c3-83d0-464a-96b0-c1708fb698f8" xlink:href="bsy-20220331.xsd#bsy_DeferredCompensationArrangementWithIndividualManagementReportOperatingIncomeFundingThreshold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsLineItems_b1d0857f-816c-4c70-a6a4-bad739916f9c" xlink:to="loc_bsy_DeferredCompensationArrangementWithIndividualManagementReportOperatingIncomeFundingThreshold_10bdd2c3-83d0-464a-96b0-c1708fb698f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_NumberOfTradingDaysPriorToEndOfApplicableQuarterSharesDeterminedUponElectionByVolumeWeightedAveragePrice_33b2da69-892e-4b89-8334-c85e135cd6e8" xlink:href="bsy-20220331.xsd#bsy_NumberOfTradingDaysPriorToEndOfApplicableQuarterSharesDeterminedUponElectionByVolumeWeightedAveragePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsLineItems_b1d0857f-816c-4c70-a6a4-bad739916f9c" xlink:to="loc_bsy_NumberOfTradingDaysPriorToEndOfApplicableQuarterSharesDeterminedUponElectionByVolumeWeightedAveragePrice_33b2da69-892e-4b89-8334-c85e135cd6e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_NumberOfTradingDaysAfterTheEndOfApplicableQuarterSharesDeterminedUponElectionByVolumeWeightedAveragePrice_b170d1a8-3491-411d-a396-a32a9a419c53" xlink:href="bsy-20220331.xsd#bsy_NumberOfTradingDaysAfterTheEndOfApplicableQuarterSharesDeterminedUponElectionByVolumeWeightedAveragePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsLineItems_b1d0857f-816c-4c70-a6a4-bad739916f9c" xlink:to="loc_bsy_NumberOfTradingDaysAfterTheEndOfApplicableQuarterSharesDeterminedUponElectionByVolumeWeightedAveragePrice_b170d1a8-3491-411d-a396-a32a9a419c53" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_NonDeferredIncentiveBonusThresholdForProRataAdjustment_6665dd51-e909-42ad-b91c-0bebabcdac15" xlink:href="bsy-20220331.xsd#bsy_NonDeferredIncentiveBonusThresholdForProRataAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsLineItems_b1d0857f-816c-4c70-a6a4-bad739916f9c" xlink:to="loc_bsy_NonDeferredIncentiveBonusThresholdForProRataAdjustment_6665dd51-e909-42ad-b91c-0bebabcdac15" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense_078e213f-e75f-4d58-b2f3-45fcfc5da6fa" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsLineItems_b1d0857f-816c-4c70-a6a4-bad739916f9c" xlink:to="loc_us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense_078e213f-e75f-4d58-b2f3-45fcfc5da6fa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsByTitleOfIndividualAndByTypeOfDeferredCompensationTable_0f618d79-c2ed-4211-ad18-0ea07da8fa1d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfDeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsByTitleOfIndividualAndByTypeOfDeferredCompensationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsLineItems_b1d0857f-816c-4c70-a6a4-bad739916f9c" xlink:to="loc_us-gaap_ScheduleOfDeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsByTitleOfIndividualAndByTypeOfDeferredCompensationTable_0f618d79-c2ed-4211-ad18-0ea07da8fa1d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsByTypeOfDeferredCompensationAxis_56d62423-8251-4812-8606-77cc5d4d86da" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsByTypeOfDeferredCompensationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsByTitleOfIndividualAndByTypeOfDeferredCompensationTable_0f618d79-c2ed-4211-ad18-0ea07da8fa1d" xlink:to="loc_us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsByTypeOfDeferredCompensationAxis_56d62423-8251-4812-8606-77cc5d4d86da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredBonusAndProfitSharingArrangementIndividualContractTypeOfDeferredCompensationDomain_56d62423-8251-4812-8606-77cc5d4d86da_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredBonusAndProfitSharingArrangementIndividualContractTypeOfDeferredCompensationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsByTypeOfDeferredCompensationAxis_56d62423-8251-4812-8606-77cc5d4d86da" xlink:to="loc_us-gaap_DeferredBonusAndProfitSharingArrangementIndividualContractTypeOfDeferredCompensationDomain_56d62423-8251-4812-8606-77cc5d4d86da_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredBonusAndProfitSharingArrangementIndividualContractTypeOfDeferredCompensationDomain_8091c750-e0ce-4ea7-a05c-54cfd0ad21f9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredBonusAndProfitSharingArrangementIndividualContractTypeOfDeferredCompensationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsByTypeOfDeferredCompensationAxis_56d62423-8251-4812-8606-77cc5d4d86da" xlink:to="loc_us-gaap_DeferredBonusAndProfitSharingArrangementIndividualContractTypeOfDeferredCompensationDomain_8091c750-e0ce-4ea7-a05c-54cfd0ad21f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredBonusMember_ff052e56-9b84-4848-ad78-a64dd12de519" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredBonusMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredBonusAndProfitSharingArrangementIndividualContractTypeOfDeferredCompensationDomain_8091c750-e0ce-4ea7-a05c-54cfd0ad21f9" xlink:to="loc_us-gaap_DeferredBonusMember_ff052e56-9b84-4848-ad78-a64dd12de519" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/RetirementPlansDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#RetirementPlansDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/RetirementPlansDetails" xlink:type="extended" id="ibf00ba2b4e2d44bb8a855685ec1a2ec9_RetirementPlansDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_35cd8a2c-a489-4f1e-a310-e7a1a2a1bbb6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DefinedContributionPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense_f7435a38-1dbe-496a-af3a-4e7ca6860c22" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_35cd8a2c-a489-4f1e-a310-e7a1a2a1bbb6" xlink:to="loc_us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense_f7435a38-1dbe-496a-af3a-4e7ca6860c22" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualDistributionPaid_bd90a3e1-b4f5-4557-adc4-035fd1ed8af2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationArrangementWithIndividualDistributionPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_35cd8a2c-a489-4f1e-a310-e7a1a2a1bbb6" xlink:to="loc_us-gaap_DeferredCompensationArrangementWithIndividualDistributionPaid_bd90a3e1-b4f5-4557-adc4-035fd1ed8af2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualContributionsByEmployer_e43bce12-2943-4d19-a6a9-f6d11e6cd38e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationArrangementWithIndividualContributionsByEmployer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_35cd8a2c-a489-4f1e-a310-e7a1a2a1bbb6" xlink:to="loc_us-gaap_DeferredCompensationArrangementWithIndividualContributionsByEmployer_e43bce12-2943-4d19-a6a9-f6d11e6cd38e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DividendsCommonStockStockIssuable_741593fb-dd15-46c4-b8a0-01c6106aec18" xlink:href="bsy-20220331.xsd#bsy_DividendsCommonStockStockIssuable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_35cd8a2c-a489-4f1e-a310-e7a1a2a1bbb6" xlink:to="loc_bsy_DividendsCommonStockStockIssuable_741593fb-dd15-46c4-b8a0-01c6106aec18" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_153fd989-867e-46e8-b41c-07b422dd0348" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_35cd8a2c-a489-4f1e-a310-e7a1a2a1bbb6" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_153fd989-867e-46e8-b41c-07b422dd0348" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent_4517d183-6b77-410c-9059-7b40a2b5fe4b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_35cd8a2c-a489-4f1e-a310-e7a1a2a1bbb6" xlink:to="loc_us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent_4517d183-6b77-410c-9059-7b40a2b5fe4b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationLiabilityCurrentAndNoncurrent_aef2bf08-1c0c-481c-80de-a17c1ac68985" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationLiabilityCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_35cd8a2c-a489-4f1e-a310-e7a1a2a1bbb6" xlink:to="loc_us-gaap_DeferredCompensationLiabilityCurrentAndNoncurrent_aef2bf08-1c0c-481c-80de-a17c1ac68985" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedContributionPlanTable_eba2ead5-9680-4cae-ab21-609a30ddc8df" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DefinedContributionPlanTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_35cd8a2c-a489-4f1e-a310-e7a1a2a1bbb6" xlink:to="loc_us-gaap_DefinedContributionPlanTable_eba2ead5-9680-4cae-ab21-609a30ddc8df" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTaxStatusAxis_0f45ad59-4b15-47c3-836e-91fc908b189d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RetirementPlanTaxStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DefinedContributionPlanTable_eba2ead5-9680-4cae-ab21-609a30ddc8df" xlink:to="loc_us-gaap_RetirementPlanTaxStatusAxis_0f45ad59-4b15-47c3-836e-91fc908b189d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTaxStatusDomain_0f45ad59-4b15-47c3-836e-91fc908b189d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RetirementPlanTaxStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTaxStatusAxis_0f45ad59-4b15-47c3-836e-91fc908b189d" xlink:to="loc_us-gaap_RetirementPlanTaxStatusDomain_0f45ad59-4b15-47c3-836e-91fc908b189d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTaxStatusDomain_e8bfa322-9eca-407b-8900-9b1a2d27fa11" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RetirementPlanTaxStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTaxStatusAxis_0f45ad59-4b15-47c3-836e-91fc908b189d" xlink:to="loc_us-gaap_RetirementPlanTaxStatusDomain_e8bfa322-9eca-407b-8900-9b1a2d27fa11" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonqualifiedPlanMember_d2072542-16ae-439e-a0e1-f3392e8a1ac7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NonqualifiedPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTaxStatusDomain_e8bfa322-9eca-407b-8900-9b1a2d27fa11" xlink:to="loc_us-gaap_NonqualifiedPlanMember_d2072542-16ae-439e-a0e1-f3392e8a1ac7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis_56bbad44-9659-4317-a7c6-454503d22355" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DefinedContributionPlanTable_eba2ead5-9680-4cae-ab21-609a30ddc8df" xlink:to="loc_us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis_56bbad44-9659-4317-a7c6-454503d22355" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitsIndividualContractsTypeOfDeferredCompensationDomain_56bbad44-9659-4317-a7c6-454503d22355_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherPostretirementBenefitsIndividualContractsTypeOfDeferredCompensationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis_56bbad44-9659-4317-a7c6-454503d22355" xlink:to="loc_us-gaap_OtherPostretirementBenefitsIndividualContractsTypeOfDeferredCompensationDomain_56bbad44-9659-4317-a7c6-454503d22355_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitsIndividualContractsTypeOfDeferredCompensationDomain_dbe459fb-ea59-4236-aa20-1f22c9b8830b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherPostretirementBenefitsIndividualContractsTypeOfDeferredCompensationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis_56bbad44-9659-4317-a7c6-454503d22355" xlink:to="loc_us-gaap_OtherPostretirementBenefitsIndividualContractsTypeOfDeferredCompensationDomain_dbe459fb-ea59-4236-aa20-1f22c9b8830b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualByTypeOfCompensationPensionAndOtherPostretirementBenefitsMember_a85df7fd-012c-4e97-89a5-3817174b5bf3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationArrangementWithIndividualByTypeOfCompensationPensionAndOtherPostretirementBenefitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherPostretirementBenefitsIndividualContractsTypeOfDeferredCompensationDomain_dbe459fb-ea59-4236-aa20-1f22c9b8830b" xlink:to="loc_us-gaap_DeferredCompensationArrangementWithIndividualByTypeOfCompensationPensionAndOtherPostretirementBenefitsMember_a85df7fd-012c-4e97-89a5-3817174b5bf3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_bd89a77b-9b7d-4c04-aad5-55cb55be075e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DefinedContributionPlanTable_eba2ead5-9680-4cae-ab21-609a30ddc8df" xlink:to="loc_us-gaap_StatementClassOfStockAxis_bd89a77b-9b7d-4c04-aad5-55cb55be075e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_bd89a77b-9b7d-4c04-aad5-55cb55be075e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_bd89a77b-9b7d-4c04-aad5-55cb55be075e" xlink:to="loc_us-gaap_ClassOfStockDomain_bd89a77b-9b7d-4c04-aad5-55cb55be075e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_d76d3569-50c4-4c0b-991b-de1d2f3071ab" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_bd89a77b-9b7d-4c04-aad5-55cb55be075e" xlink:to="loc_us-gaap_ClassOfStockDomain_d76d3569-50c4-4c0b-991b-de1d2f3071ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_d83b6e51-a244-4a3d-8015-b64c088139de" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_d76d3569-50c4-4c0b-991b-de1d2f3071ab" xlink:to="loc_us-gaap_CommonClassBMember_d83b6e51-a244-4a3d-8015-b64c088139de" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/CommonStockNarrativeDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#CommonStockNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/CommonStockNarrativeDetails" xlink:type="extended" id="id07540c656424ecd95fd4570182b8ac2_CommonStockNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodNetOfSharesWithheld_d23e2dd5-017a-4287-9ef7-3c17433cd42b" xlink:href="bsy-20220331.xsd#bsy_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodNetOfSharesWithheld"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:to="loc_bsy_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodNetOfSharesWithheld_d23e2dd5-017a-4287-9ef7-3c17433cd42b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_ShareBasedPaymentArrangementSharesWithheldForCostOfOptionsAndTaxWithholdingObligation_a78982e2-fbc6-41f7-9a35-d04e2cd085b9" xlink:href="bsy-20220331.xsd#bsy_ShareBasedPaymentArrangementSharesWithheldForCostOfOptionsAndTaxWithholdingObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:to="loc_bsy_ShareBasedPaymentArrangementSharesWithheldForCostOfOptionsAndTaxWithholdingObligation_a78982e2-fbc6-41f7-9a35-d04e2cd085b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_f9450a21-0286-427c-a278-9245a200fb22" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_f9450a21-0286-427c-a278-9245a200fb22" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards_0878c680-2638-4edd-8a9e-753bdd95e7d5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards_0878c680-2638-4edd-8a9e-753bdd95e7d5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_e0cf0ca4-d869-44d0-bd64-a4190c3c3c96" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_e0cf0ca4-d869-44d0-bd64-a4190c3c3c96" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualSharesIssued_4239bb19-aef8-45ac-ade0-ba6ee35dcb55" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationArrangementWithIndividualSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:to="loc_us-gaap_DeferredCompensationArrangementWithIndividualSharesIssued_4239bb19-aef8-45ac-ade0-ba6ee35dcb55" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DeferredCompensationArrangementWithIndividualSharesIssuedGross_e424f4a0-d60d-41a2-b55c-8b0b580a37e6" xlink:href="bsy-20220331.xsd#bsy_DeferredCompensationArrangementWithIndividualSharesIssuedGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:to="loc_bsy_DeferredCompensationArrangementWithIndividualSharesIssuedGross_e424f4a0-d60d-41a2-b55c-8b0b580a37e6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_d265080e-ab05-471b-b3d7-df5f5880bf62" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_d265080e-ab05-471b-b3d7-df5f5880bf62" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate_8509dab6-e853-41e4-a5dc-bb2b0c9611d9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate_8509dab6-e853-41e4-a5dc-bb2b0c9611d9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeAnnualContributionAmount_6a7f16e6-5e85-42c2-b3bf-77f8a8a4daae" xlink:href="bsy-20220331.xsd#bsy_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeAnnualContributionAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:to="loc_bsy_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeAnnualContributionAmount_6a7f16e6-5e85-42c2-b3bf-77f8a8a4daae" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_4bc51570-16da-4ec0-b550-e7493e565205" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_4bc51570-16da-4ec0-b550-e7493e565205" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_261b962a-2bc3-4632-94c1-ef7599c1a87a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_261b962a-2bc3-4632-94c1-ef7599c1a87a" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_0ad8fadd-0ec5-4855-a06a-6939385603ad" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_0ad8fadd-0ec5-4855-a06a-6939385603ad" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesPurchasedForAward_f6d56754-dd22-4b92-89be-0f90fb0f12f7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesPurchasedForAward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesPurchasedForAward_f6d56754-dd22-4b92-89be-0f90fb0f12f7" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherEmployeeRelatedLiabilitiesCurrent_edb2f901-9d0e-42d1-8c0a-e841c1102801" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherEmployeeRelatedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:to="loc_us-gaap_OtherEmployeeRelatedLiabilitiesCurrent_edb2f901-9d0e-42d1-8c0a-e841c1102801" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_a1cf2f7d-5561-47d6-b79c-7119ad18692d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_da34c753-25fb-4292-86a6-ab7680d96a46" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_a1cf2f7d-5561-47d6-b79c-7119ad18692d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_56d2d339-3371-4762-a16f-10e7d22beb02" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_a1cf2f7d-5561-47d6-b79c-7119ad18692d" xlink:to="loc_us-gaap_StatementClassOfStockAxis_56d2d339-3371-4762-a16f-10e7d22beb02" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_56d2d339-3371-4762-a16f-10e7d22beb02_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_56d2d339-3371-4762-a16f-10e7d22beb02" xlink:to="loc_us-gaap_ClassOfStockDomain_56d2d339-3371-4762-a16f-10e7d22beb02_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_7c4238a1-7b4c-4bc4-b8c7-1739d63326e8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_56d2d339-3371-4762-a16f-10e7d22beb02" xlink:to="loc_us-gaap_ClassOfStockDomain_7c4238a1-7b4c-4bc4-b8c7-1739d63326e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_dd09f6c6-7906-4717-8c25-e8cf9d4135ea" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_7c4238a1-7b4c-4bc4-b8c7-1739d63326e8" xlink:to="loc_us-gaap_CommonClassBMember_dd09f6c6-7906-4717-8c25-e8cf9d4135ea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_7e8cb66a-dec6-43bc-bf06-b387e26e30cc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_a1cf2f7d-5561-47d6-b79c-7119ad18692d" xlink:to="loc_us-gaap_AwardTypeAxis_7e8cb66a-dec6-43bc-bf06-b387e26e30cc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7e8cb66a-dec6-43bc-bf06-b387e26e30cc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_7e8cb66a-dec6-43bc-bf06-b387e26e30cc" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7e8cb66a-dec6-43bc-bf06-b387e26e30cc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8c097ee8-36c8-41c9-bba3-08f08cd0edac" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_7e8cb66a-dec6-43bc-bf06-b387e26e30cc" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8c097ee8-36c8-41c9-bba3-08f08cd0edac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_0071fc5d-7dfb-455b-a48c-dd8c8155066f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8c097ee8-36c8-41c9-bba3-08f08cd0edac" xlink:to="loc_us-gaap_EmployeeStockOptionMember_0071fc5d-7dfb-455b-a48c-dd8c8155066f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_bab477af-a56f-49d4-9ad8-563c832721e6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8c097ee8-36c8-41c9-bba3-08f08cd0edac" xlink:to="loc_us-gaap_EmployeeStockMember_bab477af-a56f-49d4-9ad8-563c832721e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_3902d68f-1999-42ff-8413-15aadcdfbf13" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_a1cf2f7d-5561-47d6-b79c-7119ad18692d" xlink:to="loc_us-gaap_PlanNameAxis_3902d68f-1999-42ff-8413-15aadcdfbf13" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_3902d68f-1999-42ff-8413-15aadcdfbf13_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_3902d68f-1999-42ff-8413-15aadcdfbf13" xlink:to="loc_us-gaap_PlanNameDomain_3902d68f-1999-42ff-8413-15aadcdfbf13_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_fbd6a6fb-7ac6-49cd-ad2f-05716be6922f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_3902d68f-1999-42ff-8413-15aadcdfbf13" xlink:to="loc_us-gaap_PlanNameDomain_fbd6a6fb-7ac6-49cd-ad2f-05716be6922f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_AcquisitionOptionsMember_10817721-a665-40e6-93aa-e442aef3d65e" xlink:href="bsy-20220331.xsd#bsy_AcquisitionOptionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_fbd6a6fb-7ac6-49cd-ad2f-05716be6922f" xlink:to="loc_bsy_AcquisitionOptionsMember_10817721-a665-40e6-93aa-e442aef3d65e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_BonusPlanIncentiveMember_10f0dba0-21b0-4c19-abd0-27c424e5fec5" xlink:href="bsy-20220331.xsd#bsy_BonusPlanIncentiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_fbd6a6fb-7ac6-49cd-ad2f-05716be6922f" xlink:to="loc_bsy_BonusPlanIncentiveMember_10f0dba0-21b0-4c19-abd0-27c424e5fec5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis_9ea623fc-5b1f-499a-a780-8a4e0c63905f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_a1cf2f7d-5561-47d6-b79c-7119ad18692d" xlink:to="loc_us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis_9ea623fc-5b1f-499a-a780-8a4e0c63905f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitsIndividualContractsTypeOfDeferredCompensationDomain_9ea623fc-5b1f-499a-a780-8a4e0c63905f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherPostretirementBenefitsIndividualContractsTypeOfDeferredCompensationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis_9ea623fc-5b1f-499a-a780-8a4e0c63905f" xlink:to="loc_us-gaap_OtherPostretirementBenefitsIndividualContractsTypeOfDeferredCompensationDomain_9ea623fc-5b1f-499a-a780-8a4e0c63905f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitsIndividualContractsTypeOfDeferredCompensationDomain_6a39215e-0711-4d67-8586-13f859334052" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherPostretirementBenefitsIndividualContractsTypeOfDeferredCompensationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis_9ea623fc-5b1f-499a-a780-8a4e0c63905f" xlink:to="loc_us-gaap_OtherPostretirementBenefitsIndividualContractsTypeOfDeferredCompensationDomain_6a39215e-0711-4d67-8586-13f859334052" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualByTypeOfCompensationPensionAndOtherPostretirementBenefitsMember_b74d995f-c01b-4c08-93b6-d556f9bcdd99" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationArrangementWithIndividualByTypeOfCompensationPensionAndOtherPostretirementBenefitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherPostretirementBenefitsIndividualContractsTypeOfDeferredCompensationDomain_6a39215e-0711-4d67-8586-13f859334052" xlink:to="loc_us-gaap_DeferredCompensationArrangementWithIndividualByTypeOfCompensationPensionAndOtherPostretirementBenefitsMember_b74d995f-c01b-4c08-93b6-d556f9bcdd99" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_e330ac04-ea33-483f-a8f2-c157fa9d01e6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_a1cf2f7d-5561-47d6-b79c-7119ad18692d" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_e330ac04-ea33-483f-a8f2-c157fa9d01e6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_e330ac04-ea33-483f-a8f2-c157fa9d01e6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_e330ac04-ea33-483f-a8f2-c157fa9d01e6" xlink:to="loc_us-gaap_EquityComponentDomain_e330ac04-ea33-483f-a8f2-c157fa9d01e6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_b9308530-2f8f-436e-bcf4-bb599338b3b9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_e330ac04-ea33-483f-a8f2-c157fa9d01e6" xlink:to="loc_us-gaap_EquityComponentDomain_b9308530-2f8f-436e-bcf4-bb599338b3b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_15c029f3-d57c-419c-b980-8f8ae11c3c36" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_b9308530-2f8f-436e-bcf4-bb599338b3b9" xlink:to="loc_us-gaap_CommonStockMember_15c029f3-d57c-419c-b980-8f8ae11c3c36" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/AccumulatedOtherComprehensiveLossRollforwardofAOCIDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#AccumulatedOtherComprehensiveLossRollforwardofAOCIDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/AccumulatedOtherComprehensiveLossRollforwardofAOCIDetails" xlink:type="extended" id="idef1e156e44144c7a52ba29f1e954bc8_AccumulatedOtherComprehensiveLossRollforwardofAOCIDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_51c447d1-ea69-4cd2-b31a-8d6551f862de" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_c84b7e7e-5af2-40e9-8bad-f209191fb919" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_51c447d1-ea69-4cd2-b31a-8d6551f862de" xlink:to="loc_us-gaap_StockholdersEquity_c84b7e7e-5af2-40e9-8bad-f209191fb919" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent_e0aaf7bb-66c3-4d44-8fbd-2bfdedb7859a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_51c447d1-ea69-4cd2-b31a-8d6551f862de" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent_e0aaf7bb-66c3-4d44-8fbd-2bfdedb7859a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_90598f1e-ca74-46d7-9902-d94056981657" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_51c447d1-ea69-4cd2-b31a-8d6551f862de" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_90598f1e-ca74-46d7-9902-d94056981657" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_0555c143-a386-47c0-b852-73b97d581b08" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_51c447d1-ea69-4cd2-b31a-8d6551f862de" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_0555c143-a386-47c0-b852-73b97d581b08" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_7e5899fb-4de0-47aa-bdc3-18d4860e7ee3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_549277ad-6357-42ab-9481-3f237fb861b2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_51c447d1-ea69-4cd2-b31a-8d6551f862de" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_549277ad-6357-42ab-9481-3f237fb861b2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_76502fbb-93a8-4149-86c1-7fd8888013c1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_549277ad-6357-42ab-9481-3f237fb861b2" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_76502fbb-93a8-4149-86c1-7fd8888013c1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_76502fbb-93a8-4149-86c1-7fd8888013c1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_76502fbb-93a8-4149-86c1-7fd8888013c1" xlink:to="loc_us-gaap_EquityComponentDomain_76502fbb-93a8-4149-86c1-7fd8888013c1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_0e8124f9-7feb-4454-af50-6029e9ecc8a8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_76502fbb-93a8-4149-86c1-7fd8888013c1" xlink:to="loc_us-gaap_EquityComponentDomain_0e8124f9-7feb-4454-af50-6029e9ecc8a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_9c92b42f-cb87-4e0c-8a66-3506e013a4ba" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_0e8124f9-7feb-4454-af50-6029e9ecc8a8" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_9c92b42f-cb87-4e0c-8a66-3506e013a4ba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_17c4270c-f1d6-4df1-94c9-0200baf2bca4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_9c92b42f-cb87-4e0c-8a66-3506e013a4ba" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_17c4270c-f1d6-4df1-94c9-0200baf2bca4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember_ec679fb5-2b70-4ed7-800f-b16df2380629" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_9c92b42f-cb87-4e0c-8a66-3506e013a4ba" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember_ec679fb5-2b70-4ed7-800f-b16df2380629" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/EquityAwardsandInstrumentsSummaryofStockBasedCompensationExpenseDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#EquityAwardsandInstrumentsSummaryofStockBasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/EquityAwardsandInstrumentsSummaryofStockBasedCompensationExpenseDetails" xlink:type="extended" id="i36355c9fff984f4b953aab5c85d6824b_EquityAwardsandInstrumentsSummaryofStockBasedCompensationExpenseDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_723d2675-8641-4b81-85a2-c0bdd3b16ce8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_87168991-afff-454a-b514-88849d458657" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_723d2675-8641-4b81-85a2-c0bdd3b16ce8" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_87168991-afff-454a-b514-88849d458657" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_ShareBasedPaymentArrangementExpenseAccrued_1e2b41f9-2daf-4b56-88a1-0843160e3e0e" xlink:href="bsy-20220331.xsd#bsy_ShareBasedPaymentArrangementExpenseAccrued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_723d2675-8641-4b81-85a2-c0bdd3b16ce8" xlink:to="loc_bsy_ShareBasedPaymentArrangementExpenseAccrued_1e2b41f9-2daf-4b56-88a1-0843160e3e0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_375584d1-2c40-4994-af55-eab360dc9e23" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_723d2675-8641-4b81-85a2-c0bdd3b16ce8" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_375584d1-2c40-4994-af55-eab360dc9e23" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_c37be479-ba0c-46e5-bc34-5c445a6a5fe5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_375584d1-2c40-4994-af55-eab360dc9e23" xlink:to="loc_us-gaap_AwardTypeAxis_c37be479-ba0c-46e5-bc34-5c445a6a5fe5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c37be479-ba0c-46e5-bc34-5c445a6a5fe5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_c37be479-ba0c-46e5-bc34-5c445a6a5fe5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c37be479-ba0c-46e5-bc34-5c445a6a5fe5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0b39f68a-d600-46a6-a470-abbe40b2a3ba" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_c37be479-ba0c-46e5-bc34-5c445a6a5fe5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0b39f68a-d600-46a6-a470-abbe40b2a3ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_BonusPlanMember_dbafd16a-a285-45ac-9ac2-49bc905c738f" xlink:href="bsy-20220331.xsd#bsy_BonusPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0b39f68a-d600-46a6-a470-abbe40b2a3ba" xlink:to="loc_bsy_BonusPlanMember_dbafd16a-a285-45ac-9ac2-49bc905c738f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_RestrictedStockAndRestrictedStockUnitsRSUsMember_00d88cd1-3827-4857-8f54-2a6dccac16bd" xlink:href="bsy-20220331.xsd#bsy_RestrictedStockAndRestrictedStockUnitsRSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0b39f68a-d600-46a6-a470-abbe40b2a3ba" xlink:to="loc_bsy_RestrictedStockAndRestrictedStockUnitsRSUsMember_00d88cd1-3827-4857-8f54-2a6dccac16bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_e4e8d0ab-b879-4336-aac1-c47c6abd49e5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0b39f68a-d600-46a6-a470-abbe40b2a3ba" xlink:to="loc_us-gaap_EmployeeStockOptionMember_e4e8d0ab-b879-4336-aac1-c47c6abd49e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_BentleySystemsIncorporatedGlobalEmployeeStockPurchasePlanMember_a8122c61-8241-4fda-b86d-cf3ff7608c04" xlink:href="bsy-20220331.xsd#bsy_BentleySystemsIncorporatedGlobalEmployeeStockPurchasePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0b39f68a-d600-46a6-a470-abbe40b2a3ba" xlink:to="loc_bsy_BentleySystemsIncorporatedGlobalEmployeeStockPurchasePlanMember_a8122c61-8241-4fda-b86d-cf3ff7608c04" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DeferredCompensationPlanExpenseMember_29b9a460-cb02-4513-bd2c-25631127f140" xlink:href="bsy-20220331.xsd#bsy_DeferredCompensationPlanExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0b39f68a-d600-46a6-a470-abbe40b2a3ba" xlink:to="loc_bsy_DeferredCompensationPlanExpenseMember_29b9a460-cb02-4513-bd2c-25631127f140" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_c0a0d9e5-24a8-440c-b88c-662878f750d9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_375584d1-2c40-4994-af55-eab360dc9e23" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_c0a0d9e5-24a8-440c-b88c-662878f750d9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_c0a0d9e5-24a8-440c-b88c-662878f750d9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_c0a0d9e5-24a8-440c-b88c-662878f750d9" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_c0a0d9e5-24a8-440c-b88c-662878f750d9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_29833297-9d73-464a-8ba2-4aa77bc0ac13" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_c0a0d9e5-24a8-440c-b88c-662878f750d9" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_29833297-9d73-464a-8ba2-4aa77bc0ac13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_6353bc18-d493-4a63-ba2c-f01a0bcc2e47" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_29833297-9d73-464a-8ba2-4aa77bc0ac13" xlink:to="loc_us-gaap_CostOfSalesMember_6353bc18-d493-4a63-ba2c-f01a0bcc2e47" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_4feb2571-d892-42cc-958e-974df3a367cd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_29833297-9d73-464a-8ba2-4aa77bc0ac13" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_4feb2571-d892-42cc-958e-974df3a367cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpenseMember_bf007940-e178-4c9b-85e8-6ddcdbf5b992" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SellingAndMarketingExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_29833297-9d73-464a-8ba2-4aa77bc0ac13" xlink:to="loc_us-gaap_SellingAndMarketingExpenseMember_bf007940-e178-4c9b-85e8-6ddcdbf5b992" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_b0ec9b99-ee50-4537-8b2e-2bebabc73925" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_29833297-9d73-464a-8ba2-4aa77bc0ac13" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_b0ec9b99-ee50-4537-8b2e-2bebabc73925" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_a0fc5056-4f43-427e-9eb7-71b062f8c9a0" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_375584d1-2c40-4994-af55-eab360dc9e23" xlink:to="loc_srt_ProductOrServiceAxis_a0fc5056-4f43-427e-9eb7-71b062f8c9a0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_a0fc5056-4f43-427e-9eb7-71b062f8c9a0_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_a0fc5056-4f43-427e-9eb7-71b062f8c9a0" xlink:to="loc_srt_ProductsAndServicesDomain_a0fc5056-4f43-427e-9eb7-71b062f8c9a0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_26bd11d3-5d98-49d9-b24b-7e00eb445686" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_a0fc5056-4f43-427e-9eb7-71b062f8c9a0" xlink:to="loc_srt_ProductsAndServicesDomain_26bd11d3-5d98-49d9-b24b-7e00eb445686" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_SubscriptionsAndLicensesMember_c494a1e6-a6ef-4d9f-b1f5-b3959cfcd2d2" xlink:href="bsy-20220331.xsd#bsy_SubscriptionsAndLicensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_26bd11d3-5d98-49d9-b24b-7e00eb445686" xlink:to="loc_bsy_SubscriptionsAndLicensesMember_c494a1e6-a6ef-4d9f-b1f5-b3959cfcd2d2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceMember_0f53d0c4-116b-411b-9e57-d9c3b7f832da" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_26bd11d3-5d98-49d9-b24b-7e00eb445686" xlink:to="loc_us-gaap_ServiceMember_0f53d0c4-116b-411b-9e57-d9c3b7f832da" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/EquityAwardsandInstrumentsOptionsOutstandingRollforwardDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#EquityAwardsandInstrumentsOptionsOutstandingRollforwardDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/EquityAwardsandInstrumentsOptionsOutstandingRollforwardDetails" xlink:type="extended" id="i50e095d4fa424a4f97928eb62314f9f6_EquityAwardsandInstrumentsOptionsOutstandingRollforwardDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c1209ca5-0ef5-4847-8722-9c1456e13b27" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_f3fc1ca0-15d0-4cdf-ba2a-e9afea3d5c83" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c1209ca5-0ef5-4847-8722-9c1456e13b27" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_f3fc1ca0-15d0-4cdf-ba2a-e9afea3d5c83" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_ee7c0efb-5acf-4a94-8a71-9df034f0e278" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_f3fc1ca0-15d0-4cdf-ba2a-e9afea3d5c83" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_ee7c0efb-5acf-4a94-8a71-9df034f0e278" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_653104e4-d020-4cf4-abde-a164121ce46d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_f3fc1ca0-15d0-4cdf-ba2a-e9afea3d5c83" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_653104e4-d020-4cf4-abde-a164121ce46d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_74a93eb9-77f5-44b9-8712-d6bf64f170b6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_f3fc1ca0-15d0-4cdf-ba2a-e9afea3d5c83" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_74a93eb9-77f5-44b9-8712-d6bf64f170b6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_8408303c-ead0-4d47-93f4-77f70b8f1942" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_a39ade77-de0a-4ff9-926d-4b3ebcd697de" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c1209ca5-0ef5-4847-8722-9c1456e13b27" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_a39ade77-de0a-4ff9-926d-4b3ebcd697de" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_ShareBasedPaymentArrangementByShareBasedPaymentAwardOptionsWeightedAverageExercisePricePerShareRollForward_63b05150-7819-4af4-9a92-057df6eb75cf" xlink:href="bsy-20220331.xsd#bsy_ShareBasedPaymentArrangementByShareBasedPaymentAwardOptionsWeightedAverageExercisePricePerShareRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c1209ca5-0ef5-4847-8722-9c1456e13b27" xlink:to="loc_bsy_ShareBasedPaymentArrangementByShareBasedPaymentAwardOptionsWeightedAverageExercisePricePerShareRollForward_63b05150-7819-4af4-9a92-057df6eb75cf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_ee880b38-7cfa-4d87-8ad9-6a5cda83e351" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_ShareBasedPaymentArrangementByShareBasedPaymentAwardOptionsWeightedAverageExercisePricePerShareRollForward_63b05150-7819-4af4-9a92-057df6eb75cf" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_ee880b38-7cfa-4d87-8ad9-6a5cda83e351" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_1819b63f-bea7-483f-b16b-856d8d88993f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_ShareBasedPaymentArrangementByShareBasedPaymentAwardOptionsWeightedAverageExercisePricePerShareRollForward_63b05150-7819-4af4-9a92-057df6eb75cf" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_1819b63f-bea7-483f-b16b-856d8d88993f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_df7b9eb4-2025-4037-8e5b-6b918fcec496" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_ShareBasedPaymentArrangementByShareBasedPaymentAwardOptionsWeightedAverageExercisePricePerShareRollForward_63b05150-7819-4af4-9a92-057df6eb75cf" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_df7b9eb4-2025-4037-8e5b-6b918fcec496" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_646d0e39-96e9-4401-ac43-d46ba85ae6bf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_f8f87cbf-48df-4b50-858d-cb19c4d50656" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c1209ca5-0ef5-4847-8722-9c1456e13b27" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_f8f87cbf-48df-4b50-858d-cb19c4d50656" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_fc196fff-b1db-4e74-a615-5301dbe5c372" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c1209ca5-0ef5-4847-8722-9c1456e13b27" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_fc196fff-b1db-4e74-a615-5301dbe5c372" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_9cdc65c1-d8c7-4ce3-ab5f-6171f1ce9404" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c1209ca5-0ef5-4847-8722-9c1456e13b27" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_9cdc65c1-d8c7-4ce3-ab5f-6171f1ce9404" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_8c954789-b1a6-4f46-b6e6-7099f29e6db8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c1209ca5-0ef5-4847-8722-9c1456e13b27" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_8c954789-b1a6-4f46-b6e6-7099f29e6db8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_78a99a46-cbc9-4d38-b8a3-65632613da54" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c1209ca5-0ef5-4847-8722-9c1456e13b27" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_78a99a46-cbc9-4d38-b8a3-65632613da54" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_84b0d8b2-d78f-43e2-b92d-c3fe4b1b50c6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c1209ca5-0ef5-4847-8722-9c1456e13b27" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_84b0d8b2-d78f-43e2-b92d-c3fe4b1b50c6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_76ca7f39-f44c-4496-875a-5bc011581798" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_84b0d8b2-d78f-43e2-b92d-c3fe4b1b50c6" xlink:to="loc_us-gaap_PlanNameAxis_76ca7f39-f44c-4496-875a-5bc011581798" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_76ca7f39-f44c-4496-875a-5bc011581798_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_76ca7f39-f44c-4496-875a-5bc011581798" xlink:to="loc_us-gaap_PlanNameDomain_76ca7f39-f44c-4496-875a-5bc011581798_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_fa6fefcf-6286-4343-acc8-cbe01375501b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_76ca7f39-f44c-4496-875a-5bc011581798" xlink:to="loc_us-gaap_PlanNameDomain_fa6fefcf-6286-4343-acc8-cbe01375501b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TwoThousandTwentyIncentiveAwardPlanMember_9364c5ba-9a46-40d0-890f-65b31f8f4b97" xlink:href="bsy-20220331.xsd#bsy_TwoThousandTwentyIncentiveAwardPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_fa6fefcf-6286-4343-acc8-cbe01375501b" xlink:to="loc_bsy_TwoThousandTwentyIncentiveAwardPlanMember_9364c5ba-9a46-40d0-890f-65b31f8f4b97" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_da36cbb2-ac27-4c47-8482-eed33089d967" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_84b0d8b2-d78f-43e2-b92d-c3fe4b1b50c6" xlink:to="loc_us-gaap_AwardTypeAxis_da36cbb2-ac27-4c47-8482-eed33089d967" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_da36cbb2-ac27-4c47-8482-eed33089d967_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_da36cbb2-ac27-4c47-8482-eed33089d967" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_da36cbb2-ac27-4c47-8482-eed33089d967_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2192e6f8-9878-4804-a99e-c612adf66db3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_da36cbb2-ac27-4c47-8482-eed33089d967" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2192e6f8-9878-4804-a99e-c612adf66db3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_24c3dfb5-6a1c-452b-9d5d-3b90950de31f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2192e6f8-9878-4804-a99e-c612adf66db3" xlink:to="loc_us-gaap_EmployeeStockOptionMember_24c3dfb5-6a1c-452b-9d5d-3b90950de31f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/EquityAwardsandInstrumentsStockOptionsNarrativeDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#EquityAwardsandInstrumentsStockOptionsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/EquityAwardsandInstrumentsStockOptionsNarrativeDetails" xlink:type="extended" id="id71139b2f4d74e93ac9cdfe961eef17d_EquityAwardsandInstrumentsStockOptionsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ee30793b-1488-47fa-a5d7-3b3022430b46" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromStockOptionsExercised_27e17961-0bb3-466e-b25b-6911842d882c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ee30793b-1488-47fa-a5d7-3b3022430b46" xlink:to="loc_us-gaap_ProceedsFromStockOptionsExercised_27e17961-0bb3-466e-b25b-6911842d882c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_9084c249-9538-45be-be48-54c57ee5071f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ee30793b-1488-47fa-a5d7-3b3022430b46" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_9084c249-9538-45be-be48-54c57ee5071f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_0978502b-b176-400c-9df4-ecce4254dde5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ee30793b-1488-47fa-a5d7-3b3022430b46" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_0978502b-b176-400c-9df4-ecce4254dde5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_370b4ca2-2195-4b53-ba41-d61c69241f92" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ee30793b-1488-47fa-a5d7-3b3022430b46" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_370b4ca2-2195-4b53-ba41-d61c69241f92" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_081fdf8b-7809-40eb-8682-fef9552b8826" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ee30793b-1488-47fa-a5d7-3b3022430b46" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_081fdf8b-7809-40eb-8682-fef9552b8826" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_43e3c1f3-b491-486a-8cf7-05c557961e04" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_081fdf8b-7809-40eb-8682-fef9552b8826" xlink:to="loc_us-gaap_AwardTypeAxis_43e3c1f3-b491-486a-8cf7-05c557961e04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_43e3c1f3-b491-486a-8cf7-05c557961e04_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_43e3c1f3-b491-486a-8cf7-05c557961e04" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_43e3c1f3-b491-486a-8cf7-05c557961e04_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d7f0889f-ad36-4ab7-a7a4-0cd9a3eb428c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_43e3c1f3-b491-486a-8cf7-05c557961e04" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d7f0889f-ad36-4ab7-a7a4-0cd9a3eb428c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_0c3ec197-a63f-436c-a127-719eaa02dbb5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d7f0889f-ad36-4ab7-a7a4-0cd9a3eb428c" xlink:to="loc_us-gaap_EmployeeStockOptionMember_0c3ec197-a63f-436c-a127-719eaa02dbb5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_5b742070-4af4-4ffa-812a-74652c27b15f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_081fdf8b-7809-40eb-8682-fef9552b8826" xlink:to="loc_us-gaap_PlanNameAxis_5b742070-4af4-4ffa-812a-74652c27b15f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_5b742070-4af4-4ffa-812a-74652c27b15f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_5b742070-4af4-4ffa-812a-74652c27b15f" xlink:to="loc_us-gaap_PlanNameDomain_5b742070-4af4-4ffa-812a-74652c27b15f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_9118104a-ee3d-4dda-9213-538ba057af96" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_5b742070-4af4-4ffa-812a-74652c27b15f" xlink:to="loc_us-gaap_PlanNameDomain_9118104a-ee3d-4dda-9213-538ba057af96" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TwoThousandTwentyIncentiveAwardPlanMember_364c1a48-53f2-4386-bc8c-040af67b7666" xlink:href="bsy-20220331.xsd#bsy_TwoThousandTwentyIncentiveAwardPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_9118104a-ee3d-4dda-9213-538ba057af96" xlink:to="loc_bsy_TwoThousandTwentyIncentiveAwardPlanMember_364c1a48-53f2-4386-bc8c-040af67b7666" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_EquityIncentivePlanMember_53c64239-31ac-4851-a661-0e30bac5bd77" xlink:href="bsy-20220331.xsd#bsy_EquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_9118104a-ee3d-4dda-9213-538ba057af96" xlink:to="loc_bsy_EquityIncentivePlanMember_53c64239-31ac-4851-a661-0e30bac5bd77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_4984bc07-5a9e-40a4-9eee-cec4ac8d5828" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_081fdf8b-7809-40eb-8682-fef9552b8826" xlink:to="loc_us-gaap_StatementClassOfStockAxis_4984bc07-5a9e-40a4-9eee-cec4ac8d5828" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_4984bc07-5a9e-40a4-9eee-cec4ac8d5828_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_4984bc07-5a9e-40a4-9eee-cec4ac8d5828" xlink:to="loc_us-gaap_ClassOfStockDomain_4984bc07-5a9e-40a4-9eee-cec4ac8d5828_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_5a2494ae-a215-4d91-8ec5-223b135e2fff" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_4984bc07-5a9e-40a4-9eee-cec4ac8d5828" xlink:to="loc_us-gaap_ClassOfStockDomain_5a2494ae-a215-4d91-8ec5-223b135e2fff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_6d5b46ec-51b5-40b4-8463-94e44a5f8eec" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_5a2494ae-a215-4d91-8ec5-223b135e2fff" xlink:to="loc_us-gaap_CommonClassBMember_6d5b46ec-51b5-40b4-8463-94e44a5f8eec" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/EquityAwardsandInstrumentsAcquisitionOptionsDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#EquityAwardsandInstrumentsAcquisitionOptionsDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/EquityAwardsandInstrumentsAcquisitionOptionsDetails" xlink:type="extended" id="i6ab4b1c748c34c84b494613712e18ece_EquityAwardsandInstrumentsAcquisitionOptionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c2550058-75e1-4c15-a455-892e6973dc56" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_c35d7099-12d7-41ed-867a-af6724a0d507" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c2550058-75e1-4c15-a455-892e6973dc56" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_c35d7099-12d7-41ed-867a-af6724a0d507" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_319867b6-0f52-4a34-996f-6139d8cb5890" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c2550058-75e1-4c15-a455-892e6973dc56" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_319867b6-0f52-4a34-996f-6139d8cb5890" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit_a65f6b50-7fcd-4e36-933c-8f5c0fe66845" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c2550058-75e1-4c15-a455-892e6973dc56" xlink:to="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit_a65f6b50-7fcd-4e36-933c-8f5c0fe66845" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit_b4773a1c-2075-4bfe-884c-e2d7b65176dd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c2550058-75e1-4c15-a455-892e6973dc56" xlink:to="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit_b4773a1c-2075-4bfe-884c-e2d7b65176dd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_03d5bf31-6787-45b5-a2df-67bd621ed7db" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c2550058-75e1-4c15-a455-892e6973dc56" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_03d5bf31-6787-45b5-a2df-67bd621ed7db" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_4de3b523-fc97-4e34-a52c-4751ee767909" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c2550058-75e1-4c15-a455-892e6973dc56" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_4de3b523-fc97-4e34-a52c-4751ee767909" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_bc2af2d8-551d-4cba-a3f6-db8b8da52897" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c2550058-75e1-4c15-a455-892e6973dc56" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_bc2af2d8-551d-4cba-a3f6-db8b8da52897" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_701d0c09-28a0-4667-a202-af6c31ffc268" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c2550058-75e1-4c15-a455-892e6973dc56" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_701d0c09-28a0-4667-a202-af6c31ffc268" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_38f37d57-3e97-41e2-8f9b-49cac39842f9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_701d0c09-28a0-4667-a202-af6c31ffc268" xlink:to="loc_us-gaap_AwardTypeAxis_38f37d57-3e97-41e2-8f9b-49cac39842f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_38f37d57-3e97-41e2-8f9b-49cac39842f9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_38f37d57-3e97-41e2-8f9b-49cac39842f9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_38f37d57-3e97-41e2-8f9b-49cac39842f9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4abf07ac-e8ac-4b7d-9f46-d7e60f480b58" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_38f37d57-3e97-41e2-8f9b-49cac39842f9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4abf07ac-e8ac-4b7d-9f46-d7e60f480b58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_038100a2-f058-44d3-91da-e937a87ee232" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4abf07ac-e8ac-4b7d-9f46-d7e60f480b58" xlink:to="loc_us-gaap_EmployeeStockOptionMember_038100a2-f058-44d3-91da-e937a87ee232" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_4269b755-54f0-41b6-9492-c74cc5f89e51" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_701d0c09-28a0-4667-a202-af6c31ffc268" xlink:to="loc_us-gaap_PlanNameAxis_4269b755-54f0-41b6-9492-c74cc5f89e51" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_4269b755-54f0-41b6-9492-c74cc5f89e51_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_4269b755-54f0-41b6-9492-c74cc5f89e51" xlink:to="loc_us-gaap_PlanNameDomain_4269b755-54f0-41b6-9492-c74cc5f89e51_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_4ecf485e-efe0-4d09-a38c-62eeb249215c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_4269b755-54f0-41b6-9492-c74cc5f89e51" xlink:to="loc_us-gaap_PlanNameDomain_4ecf485e-efe0-4d09-a38c-62eeb249215c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_EquityIncentivePlanMember_b8fa6356-f071-4019-983c-96cd0cce5917" xlink:href="bsy-20220331.xsd#bsy_EquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_4ecf485e-efe0-4d09-a38c-62eeb249215c" xlink:to="loc_bsy_EquityIncentivePlanMember_b8fa6356-f071-4019-983c-96cd0cce5917" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_9f31ac90-d210-4cd7-9017-93653134e052" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_701d0c09-28a0-4667-a202-af6c31ffc268" xlink:to="loc_us-gaap_StatementClassOfStockAxis_9f31ac90-d210-4cd7-9017-93653134e052" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_9f31ac90-d210-4cd7-9017-93653134e052_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_9f31ac90-d210-4cd7-9017-93653134e052" xlink:to="loc_us-gaap_ClassOfStockDomain_9f31ac90-d210-4cd7-9017-93653134e052_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_d37c4768-2a6b-49d2-b2a2-674677b658d4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_9f31ac90-d210-4cd7-9017-93653134e052" xlink:to="loc_us-gaap_ClassOfStockDomain_d37c4768-2a6b-49d2-b2a2-674677b658d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_e464e792-4ace-43ae-862d-95567c1385b1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_d37c4768-2a6b-49d2-b2a2-674677b658d4" xlink:to="loc_us-gaap_CommonClassBMember_e464e792-4ace-43ae-862d-95567c1385b1" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/EquityAwardsandInstrumentsRestrictedStockandRSUsActivityDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#EquityAwardsandInstrumentsRestrictedStockandRSUsActivityDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/EquityAwardsandInstrumentsRestrictedStockandRSUsActivityDetails" xlink:type="extended" id="i54031582a5ce40bd9d09fd5a430f8b14_EquityAwardsandInstrumentsRestrictedStockandRSUsActivityDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4021e7a4-7805-4339-bf21-3052dc5b27d5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_e9ffe71e-e3c2-46a2-a372-6a4fe86cc2a2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4021e7a4-7805-4339-bf21-3052dc5b27d5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_e9ffe71e-e3c2-46a2-a372-6a4fe86cc2a2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_6d8d04c3-fe66-4b65-91f8-2b1b1702e872" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_e9ffe71e-e3c2-46a2-a372-6a4fe86cc2a2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_6d8d04c3-fe66-4b65-91f8-2b1b1702e872" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_97a6cde4-577d-41e9-ac2f-a5aa3f1ce2b4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_e9ffe71e-e3c2-46a2-a372-6a4fe86cc2a2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_97a6cde4-577d-41e9-ac2f-a5aa3f1ce2b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_b183f496-2079-4f13-ac3a-6832701c63f2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_e9ffe71e-e3c2-46a2-a372-6a4fe86cc2a2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_b183f496-2079-4f13-ac3a-6832701c63f2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_18a070e9-bb7c-464f-9961-c8d528cc7718" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_e9ffe71e-e3c2-46a2-a372-6a4fe86cc2a2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_18a070e9-bb7c-464f-9961-c8d528cc7718" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_52997892-e85d-413f-9c05-049f56fd1f08" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_2959965b-9e85-44dd-b4eb-cec8325b5602" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4021e7a4-7805-4339-bf21-3052dc5b27d5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_2959965b-9e85-44dd-b4eb-cec8325b5602" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_d717bb17-a564-48b9-adac-6d43c273bd87" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_2959965b-9e85-44dd-b4eb-cec8325b5602" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_d717bb17-a564-48b9-adac-6d43c273bd87" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_be6f83c5-d888-45c2-985a-3d425a81af2f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_2959965b-9e85-44dd-b4eb-cec8325b5602" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_be6f83c5-d888-45c2-985a-3d425a81af2f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_b5440a75-37db-4de2-b607-f8585cfd379e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_2959965b-9e85-44dd-b4eb-cec8325b5602" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_b5440a75-37db-4de2-b607-f8585cfd379e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_2493af94-8712-4507-a7a7-004abd5615ff" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_2959965b-9e85-44dd-b4eb-cec8325b5602" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_2493af94-8712-4507-a7a7-004abd5615ff" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_32c88789-8edb-44b1-a0b9-bb7c67d77fa6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3e6c00a4-ee1c-41ae-8edd-11f55ce791d0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4021e7a4-7805-4339-bf21-3052dc5b27d5" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3e6c00a4-ee1c-41ae-8edd-11f55ce791d0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_a985c424-7fab-4d62-bd6e-2b2c07358d8f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3e6c00a4-ee1c-41ae-8edd-11f55ce791d0" xlink:to="loc_us-gaap_AwardTypeAxis_a985c424-7fab-4d62-bd6e-2b2c07358d8f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a985c424-7fab-4d62-bd6e-2b2c07358d8f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_a985c424-7fab-4d62-bd6e-2b2c07358d8f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a985c424-7fab-4d62-bd6e-2b2c07358d8f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_aaa1bfcb-821a-4ad9-a478-8707d5b24e62" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_a985c424-7fab-4d62-bd6e-2b2c07358d8f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_aaa1bfcb-821a-4ad9-a478-8707d5b24e62" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_RestrictedStockAndRestrictedStockUnitsRSUsMember_7aa2ecf8-afe0-4695-a390-ec9328271ea6" xlink:href="bsy-20220331.xsd#bsy_RestrictedStockAndRestrictedStockUnitsRSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_aaa1bfcb-821a-4ad9-a478-8707d5b24e62" xlink:to="loc_bsy_RestrictedStockAndRestrictedStockUnitsRSUsMember_7aa2ecf8-afe0-4695-a390-ec9328271ea6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TimeBasedRestrictedStockAndRestrictedStockUnitsRSUsMember_0faa88d4-0950-4bc3-9827-c4c93d4cc90e" xlink:href="bsy-20220331.xsd#bsy_TimeBasedRestrictedStockAndRestrictedStockUnitsRSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_aaa1bfcb-821a-4ad9-a478-8707d5b24e62" xlink:to="loc_bsy_TimeBasedRestrictedStockAndRestrictedStockUnitsRSUsMember_0faa88d4-0950-4bc3-9827-c4c93d4cc90e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_PerformanceBasedRestrictedStockAndRestrictedStockUnitsRSUsMember_d6590913-7001-4b8b-8aad-06c8369a61c7" xlink:href="bsy-20220331.xsd#bsy_PerformanceBasedRestrictedStockAndRestrictedStockUnitsRSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_aaa1bfcb-821a-4ad9-a478-8707d5b24e62" xlink:to="loc_bsy_PerformanceBasedRestrictedStockAndRestrictedStockUnitsRSUsMember_d6590913-7001-4b8b-8aad-06c8369a61c7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_CashSettledRestrictedStockUnitsRSUsMember_fdc68d2c-529c-46a0-9dee-b3543a154c0a" xlink:href="bsy-20220331.xsd#bsy_CashSettledRestrictedStockUnitsRSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_aaa1bfcb-821a-4ad9-a478-8707d5b24e62" xlink:to="loc_bsy_CashSettledRestrictedStockUnitsRSUsMember_fdc68d2c-529c-46a0-9dee-b3543a154c0a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TimeBasedRestrictedStockUnitsRSUsMember_57f0cf7a-3000-4502-85c5-b03f126eea88" xlink:href="bsy-20220331.xsd#bsy_TimeBasedRestrictedStockUnitsRSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_aaa1bfcb-821a-4ad9-a478-8707d5b24e62" xlink:to="loc_bsy_TimeBasedRestrictedStockUnitsRSUsMember_57f0cf7a-3000-4502-85c5-b03f126eea88" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_PerformanceBasedRestrictedStockUnitsRSUsMember_6fb87f5a-5739-4ddf-b231-92f8465dae07" xlink:href="bsy-20220331.xsd#bsy_PerformanceBasedRestrictedStockUnitsRSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_aaa1bfcb-821a-4ad9-a478-8707d5b24e62" xlink:to="loc_bsy_PerformanceBasedRestrictedStockUnitsRSUsMember_6fb87f5a-5739-4ddf-b231-92f8465dae07" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_4f9cde74-fc49-416c-a411-9add909296db" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3e6c00a4-ee1c-41ae-8edd-11f55ce791d0" xlink:to="loc_us-gaap_PlanNameAxis_4f9cde74-fc49-416c-a411-9add909296db" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_4f9cde74-fc49-416c-a411-9add909296db_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_4f9cde74-fc49-416c-a411-9add909296db" xlink:to="loc_us-gaap_PlanNameDomain_4f9cde74-fc49-416c-a411-9add909296db_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_df4f5d75-5efb-493b-ac55-59e59c9a0469" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_4f9cde74-fc49-416c-a411-9add909296db" xlink:to="loc_us-gaap_PlanNameDomain_df4f5d75-5efb-493b-ac55-59e59c9a0469" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TwoThousandTwentyIncentiveAwardPlanMember_a378cd97-e27f-4dbb-aa14-7bca786ce4af" xlink:href="bsy-20220331.xsd#bsy_TwoThousandTwentyIncentiveAwardPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_df4f5d75-5efb-493b-ac55-59e59c9a0469" xlink:to="loc_bsy_TwoThousandTwentyIncentiveAwardPlanMember_a378cd97-e27f-4dbb-aa14-7bca786ce4af" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/EquityAwardsandInstrumentsRestrictedStockandRestrictedStockUnitsNarrativeDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#EquityAwardsandInstrumentsRestrictedStockandRestrictedStockUnitsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/EquityAwardsandInstrumentsRestrictedStockandRestrictedStockUnitsNarrativeDetails" xlink:type="extended" id="i0da4d0921e9f48878f3bdf2e8921cf4c_EquityAwardsandInstrumentsRestrictedStockandRestrictedStockUnitsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_18ec7060-e09d-431e-baf5-7df0bad6b7e3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_de5f819e-934e-4f1f-ac64-fb6fd04b0eb4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_18ec7060-e09d-431e-baf5-7df0bad6b7e3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_de5f819e-934e-4f1f-ac64-fb6fd04b0eb4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSharesRealized_18e64428-2930-47fb-a738-739bc2111d83" xlink:href="bsy-20220331.xsd#bsy_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSharesRealized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_18ec7060-e09d-431e-baf5-7df0bad6b7e3" xlink:to="loc_bsy_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSharesRealized_18e64428-2930-47fb-a738-739bc2111d83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsDeliveredInPeriod_aafae2bc-72d1-480c-a0d7-c48d79d39af3" xlink:href="bsy-20220331.xsd#bsy_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsDeliveredInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_18ec7060-e09d-431e-baf5-7df0bad6b7e3" xlink:to="loc_bsy_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsDeliveredInPeriod_aafae2bc-72d1-480c-a0d7-c48d79d39af3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsEarnedThroughDividendsInPeriod_1914eb5b-4ee5-4c00-998c-07001a64af74" xlink:href="bsy-20220331.xsd#bsy_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsEarnedThroughDividendsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_18ec7060-e09d-431e-baf5-7df0bad6b7e3" xlink:to="loc_bsy_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsEarnedThroughDividendsInPeriod_1914eb5b-4ee5-4c00-998c-07001a64af74" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_b9097fa6-62f6-4088-8842-ba4735240331" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_18ec7060-e09d-431e-baf5-7df0bad6b7e3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_b9097fa6-62f6-4088-8842-ba4735240331" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_7ce0ae5a-066f-46be-908e-1909540a7205" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_18ec7060-e09d-431e-baf5-7df0bad6b7e3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_7ce0ae5a-066f-46be-908e-1909540a7205" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_3a9b1ef5-b9c3-4e9e-9b64-4434c922b9f2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_18ec7060-e09d-431e-baf5-7df0bad6b7e3" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_3a9b1ef5-b9c3-4e9e-9b64-4434c922b9f2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsShareBasedLiabilitiesPaid_1ea73b77-cd78-4af8-aee8-70e18ca47e6b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsShareBasedLiabilitiesPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_18ec7060-e09d-431e-baf5-7df0bad6b7e3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsShareBasedLiabilitiesPaid_1ea73b77-cd78-4af8-aee8-70e18ca47e6b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_045ceb21-66ea-4b2f-b6b1-788d178653d6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_18ec7060-e09d-431e-baf5-7df0bad6b7e3" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_045ceb21-66ea-4b2f-b6b1-788d178653d6" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_3ce523fc-29d5-4190-98a3-d2e93404c72c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_18ec7060-e09d-431e-baf5-7df0bad6b7e3" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_3ce523fc-29d5-4190-98a3-d2e93404c72c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_a8e25036-b6eb-44d8-bf48-a5e920d401fe" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_18ec7060-e09d-431e-baf5-7df0bad6b7e3" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_a8e25036-b6eb-44d8-bf48-a5e920d401fe" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_417b9907-b934-445b-a9ff-54ccda33179b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_a8e25036-b6eb-44d8-bf48-a5e920d401fe" xlink:to="loc_us-gaap_AwardTypeAxis_417b9907-b934-445b-a9ff-54ccda33179b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_417b9907-b934-445b-a9ff-54ccda33179b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_417b9907-b934-445b-a9ff-54ccda33179b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_417b9907-b934-445b-a9ff-54ccda33179b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_93117af5-9252-4d1f-a9f1-b0a19e1cbc60" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_417b9907-b934-445b-a9ff-54ccda33179b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_93117af5-9252-4d1f-a9f1-b0a19e1cbc60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_PerformanceBasedRestrictedStockUnitsRSUsMember_51545e97-1c56-44a0-90c9-2618621cc89d" xlink:href="bsy-20220331.xsd#bsy_PerformanceBasedRestrictedStockUnitsRSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_93117af5-9252-4d1f-a9f1-b0a19e1cbc60" xlink:to="loc_bsy_PerformanceBasedRestrictedStockUnitsRSUsMember_51545e97-1c56-44a0-90c9-2618621cc89d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_PerformanceBasedRestrictedStockUnitsRSUsTwoThousandSixteenMember_e85b800d-5240-4d4a-bcc7-01b19410bf4b" xlink:href="bsy-20220331.xsd#bsy_PerformanceBasedRestrictedStockUnitsRSUsTwoThousandSixteenMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_93117af5-9252-4d1f-a9f1-b0a19e1cbc60" xlink:to="loc_bsy_PerformanceBasedRestrictedStockUnitsRSUsTwoThousandSixteenMember_e85b800d-5240-4d4a-bcc7-01b19410bf4b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_9a984209-d6f7-4cea-832d-2764da449d64" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_93117af5-9252-4d1f-a9f1-b0a19e1cbc60" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_9a984209-d6f7-4cea-832d-2764da449d64" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_RestrictedStockAndRestrictedStockUnitsRSUsMember_78da4f01-1740-42e6-b436-45f99c2b3858" xlink:href="bsy-20220331.xsd#bsy_RestrictedStockAndRestrictedStockUnitsRSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_93117af5-9252-4d1f-a9f1-b0a19e1cbc60" xlink:to="loc_bsy_RestrictedStockAndRestrictedStockUnitsRSUsMember_78da4f01-1740-42e6-b436-45f99c2b3858" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TimeBasedRestrictedStockAndRestrictedStockUnitsRSUsMember_ee985d9c-300c-417f-a8ea-2e24e08e4292" xlink:href="bsy-20220331.xsd#bsy_TimeBasedRestrictedStockAndRestrictedStockUnitsRSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_93117af5-9252-4d1f-a9f1-b0a19e1cbc60" xlink:to="loc_bsy_TimeBasedRestrictedStockAndRestrictedStockUnitsRSUsMember_ee985d9c-300c-417f-a8ea-2e24e08e4292" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_3a3b57d5-64bf-4b96-bba9-cac01ed8636e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_a8e25036-b6eb-44d8-bf48-a5e920d401fe" xlink:to="loc_us-gaap_PlanNameAxis_3a3b57d5-64bf-4b96-bba9-cac01ed8636e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_3a3b57d5-64bf-4b96-bba9-cac01ed8636e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_3a3b57d5-64bf-4b96-bba9-cac01ed8636e" xlink:to="loc_us-gaap_PlanNameDomain_3a3b57d5-64bf-4b96-bba9-cac01ed8636e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_095b0a87-652e-48e5-911c-f73532e2d727" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_3a3b57d5-64bf-4b96-bba9-cac01ed8636e" xlink:to="loc_us-gaap_PlanNameDomain_095b0a87-652e-48e5-911c-f73532e2d727" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TwoThousandTwentyIncentiveAwardPlanMember_8602bed1-c0c5-4f52-b9d2-ce2d87506362" xlink:href="bsy-20220331.xsd#bsy_TwoThousandTwentyIncentiveAwardPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_095b0a87-652e-48e5-911c-f73532e2d727" xlink:to="loc_bsy_TwoThousandTwentyIncentiveAwardPlanMember_8602bed1-c0c5-4f52-b9d2-ce2d87506362" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingAxis_df23d34d-27f6-40b6-9299-7fe79df9bc3b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_VestingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_a8e25036-b6eb-44d8-bf48-a5e920d401fe" xlink:to="loc_us-gaap_VestingAxis_df23d34d-27f6-40b6-9299-7fe79df9bc3b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_df23d34d-27f6-40b6-9299-7fe79df9bc3b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_df23d34d-27f6-40b6-9299-7fe79df9bc3b" xlink:to="loc_us-gaap_VestingDomain_df23d34d-27f6-40b6-9299-7fe79df9bc3b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_8c723528-8dcf-404a-abf8-34e52d93ac7d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_df23d34d-27f6-40b6-9299-7fe79df9bc3b" xlink:to="loc_us-gaap_VestingDomain_8c723528-8dcf-404a-abf8-34e52d93ac7d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_PerformanceBasedVestingMember_d6a419e4-1ec8-4700-8e82-638189118082" xlink:href="bsy-20220331.xsd#bsy_PerformanceBasedVestingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_8c723528-8dcf-404a-abf8-34e52d93ac7d" xlink:to="loc_bsy_PerformanceBasedVestingMember_d6a419e4-1ec8-4700-8e82-638189118082" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/IncomeTaxesNarrativeDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#IncomeTaxesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/IncomeTaxesNarrativeDetails" xlink:type="extended" id="i5734fef622de4d9b8a54b0ab5371a512_IncomeTaxesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLossCarryforwardsLineItems_4e83a74a-a7c6-4c1a-bd41-b067d43b1bab" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLossCarryforwardsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_05afc7d8-818c-4eda-9da4-44c14f4a46ab" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_4e83a74a-a7c6-4c1a-bd41-b067d43b1bab" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_05afc7d8-818c-4eda-9da4-44c14f4a46ab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DiscreteIncomeTaxExpenseBenefit_700be622-de68-4870-8ab9-ca1e24dea1d9" xlink:href="bsy-20220331.xsd#bsy_DiscreteIncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_4e83a74a-a7c6-4c1a-bd41-b067d43b1bab" xlink:to="loc_bsy_DiscreteIncomeTaxExpenseBenefit_700be622-de68-4870-8ab9-ca1e24dea1d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_0cf912ec-1d1c-418d-a694-6c09ee9d48be" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_4e83a74a-a7c6-4c1a-bd41-b067d43b1bab" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_0cf912ec-1d1c-418d-a694-6c09ee9d48be" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_de6bf646-f234-4935-8cce-f003efccf118" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_4e83a74a-a7c6-4c1a-bd41-b067d43b1bab" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_de6bf646-f234-4935-8cce-f003efccf118" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UndistributedEarningsOfForeignSubsidiaries_df90a8cf-0ed8-46e2-a9bb-c9037440baf3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_UndistributedEarningsOfForeignSubsidiaries"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_4e83a74a-a7c6-4c1a-bd41-b067d43b1bab" xlink:to="loc_us-gaap_UndistributedEarningsOfForeignSubsidiaries_df90a8cf-0ed8-46e2-a9bb-c9037440baf3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignEarningsRepatriated_8efe994f-d18d-480f-bfed-d42079d9e6e9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignEarningsRepatriated"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_4e83a74a-a7c6-4c1a-bd41-b067d43b1bab" xlink:to="loc_us-gaap_ForeignEarningsRepatriated_8efe994f-d18d-480f-bfed-d42079d9e6e9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLossCarryforwardsTable_1ce78e30-502b-43bb-a002-8a3725ce8629" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLossCarryforwardsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_4e83a74a-a7c6-4c1a-bd41-b067d43b1bab" xlink:to="loc_us-gaap_OperatingLossCarryforwardsTable_1ce78e30-502b-43bb-a002-8a3725ce8629" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_380a02bb-2455-48da-93d2-b02aa82d6168" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OperatingLossCarryforwardsTable_1ce78e30-502b-43bb-a002-8a3725ce8629" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_380a02bb-2455-48da-93d2-b02aa82d6168" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_380a02bb-2455-48da-93d2-b02aa82d6168_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_380a02bb-2455-48da-93d2-b02aa82d6168" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_380a02bb-2455-48da-93d2-b02aa82d6168_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_a4a59661-30f3-4e03-a224-8e1b48c1a6cf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_380a02bb-2455-48da-93d2-b02aa82d6168" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_a4a59661-30f3-4e03-a224-8e1b48c1a6cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_395586a1-d75f-408f-a5e4-13d0fc8aeecf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_a4a59661-30f3-4e03-a224-8e1b48c1a6cf" xlink:to="loc_us-gaap_SubsequentEventMember_395586a1-d75f-408f-a5e4-13d0fc8aeecf" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/FairValueofFinancialInstrumentsNarrativeDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#FairValueofFinancialInstrumentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/FairValueofFinancialInstrumentsNarrativeDetails" xlink:type="extended" id="i26f534e6e8684aaa8199b2c1cf61627c_FairValueofFinancialInstrumentsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_ef9519f5-d24f-4704-b8a3-a621f0a6be67" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityNotionalAmount_fc6a4882-0dd1-47c7-978c-cc093b2e69e5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeLiabilityNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_ef9519f5-d24f-4704-b8a3-a621f0a6be67" xlink:to="loc_us-gaap_DerivativeLiabilityNotionalAmount_fc6a4882-0dd1-47c7-978c-cc093b2e69e5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_ef516c83-d5ed-4c7d-a3e0-79d617681412" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_ef9519f5-d24f-4704-b8a3-a621f0a6be67" xlink:to="loc_us-gaap_LongTermDebtFairValue_ef516c83-d5ed-4c7d-a3e0-79d617681412" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_a4a286dd-87f9-4861-a9d7-fdbb222ec0c8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_ef9519f5-d24f-4704-b8a3-a621f0a6be67" xlink:to="loc_us-gaap_DerivativeTable_a4a286dd-87f9-4861-a9d7-fdbb222ec0c8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_6b61e44d-e9da-42d5-9a25-56328de00257" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_a4a286dd-87f9-4861-a9d7-fdbb222ec0c8" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_6b61e44d-e9da-42d5-9a25-56328de00257" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_6b61e44d-e9da-42d5-9a25-56328de00257_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_6b61e44d-e9da-42d5-9a25-56328de00257" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_6b61e44d-e9da-42d5-9a25-56328de00257_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_42e5120f-fe1d-46c2-a530-41d8b5905483" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_6b61e44d-e9da-42d5-9a25-56328de00257" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_42e5120f-fe1d-46c2-a530-41d8b5905483" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_10d7417e-8730-454b-a49f-a775e5ed9f88" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_42e5120f-fe1d-46c2-a530-41d8b5905483" xlink:to="loc_us-gaap_InterestRateSwapMember_10d7417e-8730-454b-a49f-a775e5ed9f88" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_f39dabad-0d65-4589-bef6-ee543de741ae" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_a4a286dd-87f9-4861-a9d7-fdbb222ec0c8" xlink:to="loc_us-gaap_HedgingDesignationAxis_f39dabad-0d65-4589-bef6-ee543de741ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_f39dabad-0d65-4589-bef6-ee543de741ae_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_f39dabad-0d65-4589-bef6-ee543de741ae" xlink:to="loc_us-gaap_HedgingDesignationDomain_f39dabad-0d65-4589-bef6-ee543de741ae_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_a9374cd0-bad5-4114-8705-df50fa81f156" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_f39dabad-0d65-4589-bef6-ee543de741ae" xlink:to="loc_us-gaap_HedgingDesignationDomain_a9374cd0-bad5-4114-8705-df50fa81f156" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_148c218c-8c3c-4179-964f-e1051f53de62" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_a9374cd0-bad5-4114-8705-df50fa81f156" xlink:to="loc_us-gaap_NondesignatedMember_148c218c-8c3c-4179-964f-e1051f53de62" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_35a14bfc-a417-453b-bbdb-2b8956f927de" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_a4a286dd-87f9-4861-a9d7-fdbb222ec0c8" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_35a14bfc-a417-453b-bbdb-2b8956f927de" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_35a14bfc-a417-453b-bbdb-2b8956f927de_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_35a14bfc-a417-453b-bbdb-2b8956f927de" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_35a14bfc-a417-453b-bbdb-2b8956f927de_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_16639a0d-d8c0-43cd-9930-fca46bdde8a7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_35a14bfc-a417-453b-bbdb-2b8956f927de" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_16639a0d-d8c0-43cd-9930-fca46bdde8a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_d99e7fbc-2e5f-4e30-a733-e08e5752ade2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_16639a0d-d8c0-43cd-9930-fca46bdde8a7" xlink:to="loc_us-gaap_ConvertibleDebtMember_d99e7fbc-2e5f-4e30-a733-e08e5752ade2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_8819baaa-d693-465a-89bf-f7cbbcd8c8bc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_a4a286dd-87f9-4861-a9d7-fdbb222ec0c8" xlink:to="loc_us-gaap_DebtInstrumentAxis_8819baaa-d693-465a-89bf-f7cbbcd8c8bc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_8819baaa-d693-465a-89bf-f7cbbcd8c8bc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_8819baaa-d693-465a-89bf-f7cbbcd8c8bc" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_8819baaa-d693-465a-89bf-f7cbbcd8c8bc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_880324c6-6a42-447f-8b37-dae2f3c0d7be" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_8819baaa-d693-465a-89bf-f7cbbcd8c8bc" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_880324c6-6a42-447f-8b37-dae2f3c0d7be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TwoThousandTwentySixNotesMember_9a0c460b-5389-44bd-bb9a-73cb851eef9c" xlink:href="bsy-20220331.xsd#bsy_TwoThousandTwentySixNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_880324c6-6a42-447f-8b37-dae2f3c0d7be" xlink:to="loc_bsy_TwoThousandTwentySixNotesMember_9a0c460b-5389-44bd-bb9a-73cb851eef9c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TwoThousandTwentySevenNotesMember_0fed232b-07d4-4f88-be5c-57c4e9594434" xlink:href="bsy-20220331.xsd#bsy_TwoThousandTwentySevenNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_880324c6-6a42-447f-8b37-dae2f3c0d7be" xlink:to="loc_bsy_TwoThousandTwentySevenNotesMember_0fed232b-07d4-4f88-be5c-57c4e9594434" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_7b99751f-fb58-4f3a-819c-481dca6884aa" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_a4a286dd-87f9-4861-a9d7-fdbb222ec0c8" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_7b99751f-fb58-4f3a-819c-481dca6884aa" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7b99751f-fb58-4f3a-819c-481dca6884aa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_7b99751f-fb58-4f3a-819c-481dca6884aa" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7b99751f-fb58-4f3a-819c-481dca6884aa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1157e961-bb7e-476c-94c0-8b2e149116cb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_7b99751f-fb58-4f3a-819c-481dca6884aa" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1157e961-bb7e-476c-94c0-8b2e149116cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_f3d7876f-cfd0-4116-afe7-913721c32427" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1157e961-bb7e-476c-94c0-8b2e149116cb" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_f3d7876f-cfd0-4116-afe7-913721c32427" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/FairValueofFinancialInstrumentsInterestRateSwapActivityDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#FairValueofFinancialInstrumentsInterestRateSwapActivityDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/FairValueofFinancialInstrumentsInterestRateSwapActivityDetails" xlink:type="extended" id="i7c4d27949aff42fcb010aa9dcfca0051_FairValueofFinancialInstrumentsInterestRateSwapActivityDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_042267b3-ebd8-4962-8222-27482178712d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_67fe402b-89ec-463e-9d61-05eda6ee6802" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_042267b3-ebd8-4962-8222-27482178712d" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_67fe402b-89ec-463e-9d61-05eda6ee6802" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsPayments_b226b05a-776b-4e46-a193-3139ed5a3902" xlink:href="bsy-20220331.xsd#bsy_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsPayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_042267b3-ebd8-4962-8222-27482178712d" xlink:to="loc_bsy_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsPayments_b226b05a-776b-4e46-a193-3139ed5a3902" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_95201c22-e695-4869-81f7-df74fe0d0838" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_042267b3-ebd8-4962-8222-27482178712d" xlink:to="loc_us-gaap_DerivativeTable_95201c22-e695-4869-81f7-df74fe0d0838" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_483d1c51-e828-4b4b-9ad0-61d3428fa771" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_95201c22-e695-4869-81f7-df74fe0d0838" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_483d1c51-e828-4b4b-9ad0-61d3428fa771" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_483d1c51-e828-4b4b-9ad0-61d3428fa771_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_483d1c51-e828-4b4b-9ad0-61d3428fa771" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_483d1c51-e828-4b4b-9ad0-61d3428fa771_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_7eec43a4-acb5-46d1-b84a-a545a34109eb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_483d1c51-e828-4b4b-9ad0-61d3428fa771" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_7eec43a4-acb5-46d1-b84a-a545a34109eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_2d010b97-f070-46d0-8dbe-5fef1a7638b1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_7eec43a4-acb5-46d1-b84a-a545a34109eb" xlink:to="loc_us-gaap_InterestRateSwapMember_2d010b97-f070-46d0-8dbe-5fef1a7638b1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_9ec15c3a-b187-4b89-9015-b7c6fb052b7a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_95201c22-e695-4869-81f7-df74fe0d0838" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_9ec15c3a-b187-4b89-9015-b7c6fb052b7a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_9ec15c3a-b187-4b89-9015-b7c6fb052b7a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_9ec15c3a-b187-4b89-9015-b7c6fb052b7a" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_9ec15c3a-b187-4b89-9015-b7c6fb052b7a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_aeb304d9-37c3-4429-b690-a90113f0921f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_9ec15c3a-b187-4b89-9015-b7c6fb052b7a" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_aeb304d9-37c3-4429-b690-a90113f0921f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpenseMember_01035923-cc31-4757-a251-8d774afdeb7f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_aeb304d9-37c3-4429-b690-a90113f0921f" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpenseMember_01035923-cc31-4757-a251-8d774afdeb7f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseMember_d872b910-2f85-4e32-b5b8-f82a5683f91b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_aeb304d9-37c3-4429-b690-a90113f0921f" xlink:to="loc_us-gaap_InterestExpenseMember_d872b910-2f85-4e32-b5b8-f82a5683f91b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/FairValueofFinancialInstrumentsFairValueofFinancialAssetsandLiabilitiesDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#FairValueofFinancialInstrumentsFairValueofFinancialAssetsandLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/FairValueofFinancialInstrumentsFairValueofFinancialAssetsandLiabilitiesDetails" xlink:type="extended" id="i4f18b752d2874caeb2191f60d53470b2_FairValueofFinancialInstrumentsFairValueofFinancialAssetsandLiabilitiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_f964ac6f-4f45-4fc6-9140-f7e3e655e545" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_a68320a7-3461-4364-be22-59b0d6822c1d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_f964ac6f-4f45-4fc6-9140-f7e3e655e545" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_a68320a7-3461-4364-be22-59b0d6822c1d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_b857d5a3-1936-4cb1-81fb-3f34f56b834d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_a68320a7-3461-4364-be22-59b0d6822c1d" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_b857d5a3-1936-4cb1-81fb-3f34f56b834d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_eaff8e30-8b98-46b1-93f9-2b316dde4388" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_a68320a7-3461-4364-be22-59b0d6822c1d" xlink:to="loc_us-gaap_DerivativeAssets_eaff8e30-8b98-46b1-93f9-2b316dde4388" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_72b4bbe1-c7be-4817-a95d-7fd09fbe1510" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_a68320a7-3461-4364-be22-59b0d6822c1d" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_72b4bbe1-c7be-4817-a95d-7fd09fbe1510" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_96cd17a3-fa1e-4a79-a968-a70c1367e094" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_f964ac6f-4f45-4fc6-9140-f7e3e655e545" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_96cd17a3-fa1e-4a79-a968-a70c1367e094" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_52006377-6666-4998-9036-548ad1fa29fb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_96cd17a3-fa1e-4a79-a968-a70c1367e094" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_52006377-6666-4998-9036-548ad1fa29fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DeferredCompensationLiabilityFairValueDisclosure_121f22dd-47c7-4619-9b8d-609d72abb111" xlink:href="bsy-20220331.xsd#bsy_DeferredCompensationLiabilityFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_96cd17a3-fa1e-4a79-a968-a70c1367e094" xlink:to="loc_bsy_DeferredCompensationLiabilityFairValueDisclosure_121f22dd-47c7-4619-9b8d-609d72abb111" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_AccruedEquityBasedCompensationFairValueDisclosure_175d38ef-f936-4e57-b28c-60a6144fdddc" xlink:href="bsy-20220331.xsd#bsy_AccruedEquityBasedCompensationFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_96cd17a3-fa1e-4a79-a968-a70c1367e094" xlink:to="loc_bsy_AccruedEquityBasedCompensationFairValueDisclosure_175d38ef-f936-4e57-b28c-60a6144fdddc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_27ede80a-bdcf-4b53-9096-b3d2d07d60a5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_96cd17a3-fa1e-4a79-a968-a70c1367e094" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_27ede80a-bdcf-4b53-9096-b3d2d07d60a5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_a8d3e316-cd48-4daf-ae97-a31837caa790" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_f964ac6f-4f45-4fc6-9140-f7e3e655e545" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_a8d3e316-cd48-4daf-ae97-a31837caa790" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DeferredCompensationLiabilityFairValueDisclosureCurrent_c30e97da-8ed7-435c-9aa2-18bfae0174b5" xlink:href="bsy-20220331.xsd#bsy_DeferredCompensationLiabilityFairValueDisclosureCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_f964ac6f-4f45-4fc6-9140-f7e3e655e545" xlink:to="loc_bsy_DeferredCompensationLiabilityFairValueDisclosureCurrent_c30e97da-8ed7-435c-9aa2-18bfae0174b5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_9726b595-18ba-43ef-b27b-4b3f03a21f0d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_f964ac6f-4f45-4fc6-9140-f7e3e655e545" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_9726b595-18ba-43ef-b27b-4b3f03a21f0d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_6259a2cb-2644-43b7-8cd0-74f9264d9779" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_9726b595-18ba-43ef-b27b-4b3f03a21f0d" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_6259a2cb-2644-43b7-8cd0-74f9264d9779" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_6259a2cb-2644-43b7-8cd0-74f9264d9779_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_6259a2cb-2644-43b7-8cd0-74f9264d9779" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_6259a2cb-2644-43b7-8cd0-74f9264d9779_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_612c1152-e509-473a-8942-e4bbf0212f9d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_6259a2cb-2644-43b7-8cd0-74f9264d9779" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_612c1152-e509-473a-8942-e4bbf0212f9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_c2bf598d-d72f-45ad-8c30-73381a968cc7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_612c1152-e509-473a-8942-e4bbf0212f9d" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_c2bf598d-d72f-45ad-8c30-73381a968cc7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_dc938fbb-30c6-4d25-af77-50dac5e51d34" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_612c1152-e509-473a-8942-e4bbf0212f9d" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_dc938fbb-30c6-4d25-af77-50dac5e51d34" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_bc8e3f60-6ef6-4b32-b334-3d742f3b76e2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_612c1152-e509-473a-8942-e4bbf0212f9d" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_bc8e3f60-6ef6-4b32-b334-3d742f3b76e2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_ccd84ad1-9e72-4349-89a5-f28d8de2c0c6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_9726b595-18ba-43ef-b27b-4b3f03a21f0d" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_ccd84ad1-9e72-4349-89a5-f28d8de2c0c6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_ccd84ad1-9e72-4349-89a5-f28d8de2c0c6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_ccd84ad1-9e72-4349-89a5-f28d8de2c0c6" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_ccd84ad1-9e72-4349-89a5-f28d8de2c0c6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_c96f1dd7-9dc4-4827-847b-aedc195209c5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_ccd84ad1-9e72-4349-89a5-f28d8de2c0c6" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_c96f1dd7-9dc4-4827-847b-aedc195209c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_f437a2ad-544f-4b2f-a6bf-6a07b6f2ea9f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_c96f1dd7-9dc4-4827-847b-aedc195209c5" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_f437a2ad-544f-4b2f-a6bf-6a07b6f2ea9f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_5ca29003-7f4c-4b0c-a66b-0df0997704c3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_9726b595-18ba-43ef-b27b-4b3f03a21f0d" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_5ca29003-7f4c-4b0c-a66b-0df0997704c3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_5ca29003-7f4c-4b0c-a66b-0df0997704c3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_5ca29003-7f4c-4b0c-a66b-0df0997704c3" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_5ca29003-7f4c-4b0c-a66b-0df0997704c3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_aa3b4cf9-1f48-439c-ae46-f6d5f410869d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_5ca29003-7f4c-4b0c-a66b-0df0997704c3" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_aa3b4cf9-1f48-439c-ae46-f6d5f410869d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_bc262005-5bf6-4fef-a125-3235dd45865d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_aa3b4cf9-1f48-439c-ae46-f6d5f410869d" xlink:to="loc_us-gaap_MoneyMarketFundsMember_bc262005-5bf6-4fef-a125-3235dd45865d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_ac3ec013-7165-466a-a552-b9b759f3cfbe" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_9726b595-18ba-43ef-b27b-4b3f03a21f0d" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_ac3ec013-7165-466a-a552-b9b759f3cfbe" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_ac3ec013-7165-466a-a552-b9b759f3cfbe_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_ac3ec013-7165-466a-a552-b9b759f3cfbe" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_ac3ec013-7165-466a-a552-b9b759f3cfbe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_b10e14a8-5fbf-4720-b513-75cc4fdc93cd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_ac3ec013-7165-466a-a552-b9b759f3cfbe" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_b10e14a8-5fbf-4720-b513-75cc4fdc93cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_fbe9302b-1cde-4e55-91c6-5f50f128a0e6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_b10e14a8-5fbf-4720-b513-75cc4fdc93cd" xlink:to="loc_us-gaap_InterestRateSwapMember_fbe9302b-1cde-4e55-91c6-5f50f128a0e6" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/CommitmentsandContingenciesDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#CommitmentsandContingenciesDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/CommitmentsandContingenciesDetails" xlink:type="extended" id="i9e0dc6564583464a8941c4cf90ebf8b1_CommitmentsandContingenciesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentLineItems_53f30336-01d3-4eeb-a090-c316da43fb39" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermPurchaseCommitmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentAmount_7ca30071-f368-402a-81e5-b5f7402b30e1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermPurchaseCommitmentAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_53f30336-01d3-4eeb-a090-c316da43fb39" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentAmount_7ca30071-f368-402a-81e5-b5f7402b30e1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentTable_0393d301-8399-4aab-a645-78b754056b19" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermPurchaseCommitmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_53f30336-01d3-4eeb-a090-c316da43fb39" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentTable_0393d301-8399-4aab-a645-78b754056b19" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_66e459fb-ba2d-465d-931d-ed2e7b55b9c5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_0393d301-8399-4aab-a645-78b754056b19" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_66e459fb-ba2d-465d-931d-ed2e7b55b9c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_66e459fb-ba2d-465d-931d-ed2e7b55b9c5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_66e459fb-ba2d-465d-931d-ed2e7b55b9c5" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_66e459fb-ba2d-465d-931d-ed2e7b55b9c5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_5a9b6fe5-9c42-47e6-9423-91c0ecb0b64b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_66e459fb-ba2d-465d-931d-ed2e7b55b9c5" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_5a9b6fe5-9c42-47e6-9423-91c0ecb0b64b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_HostedSoftwareSolutionsMember_42014f4f-597d-4488-982d-6fd2eca70f4d" xlink:href="bsy-20220331.xsd#bsy_HostedSoftwareSolutionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_5a9b6fe5-9c42-47e6-9423-91c0ecb0b64b" xlink:to="loc_bsy_HostedSoftwareSolutionsMember_42014f4f-597d-4488-982d-6fd2eca70f4d" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/GeographicDataDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#GeographicDataDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/GeographicDataDetails" xlink:type="extended" id="i5e0f28eab6a340c2a792217f99f44979_GeographicDataDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_323fc19d-372c-454b-8797-3d3f08d6c392" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncurrentAssets_75f87ac7-0f48-4a80-82fa-7f1d64d96cc0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_323fc19d-372c-454b-8797-3d3f08d6c392" xlink:to="loc_us-gaap_NoncurrentAssets_75f87ac7-0f48-4a80-82fa-7f1d64d96cc0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_8ee84169-c5e7-4774-be21-8d2ee675e1ce" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_323fc19d-372c-454b-8797-3d3f08d6c392" xlink:to="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_8ee84169-c5e7-4774-be21-8d2ee675e1ce" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_8503b743-d8f2-4b80-9244-325100228019" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_8ee84169-c5e7-4774-be21-8d2ee675e1ce" xlink:to="loc_srt_StatementGeographicalAxis_8503b743-d8f2-4b80-9244-325100228019" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_8503b743-d8f2-4b80-9244-325100228019_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_8503b743-d8f2-4b80-9244-325100228019" xlink:to="loc_srt_SegmentGeographicalDomain_8503b743-d8f2-4b80-9244-325100228019_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_30b7140e-50c1-4ecf-b064-6610eb400fc9" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_8503b743-d8f2-4b80-9244-325100228019" xlink:to="loc_srt_SegmentGeographicalDomain_30b7140e-50c1-4ecf-b064-6610eb400fc9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_UnitedStatesCanadaLatinAmericaAndCaribbeanMember_984c5c5d-9a64-4fbd-8c14-6515f2a537ff" xlink:href="bsy-20220331.xsd#bsy_UnitedStatesCanadaLatinAmericaAndCaribbeanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_30b7140e-50c1-4ecf-b064-6610eb400fc9" xlink:to="loc_bsy_UnitedStatesCanadaLatinAmericaAndCaribbeanMember_984c5c5d-9a64-4fbd-8c14-6515f2a537ff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EMEAMember_a77cfa86-436c-40c8-8d08-f2636edc915f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EMEAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_30b7140e-50c1-4ecf-b064-6610eb400fc9" xlink:to="loc_us-gaap_EMEAMember_a77cfa86-436c-40c8-8d08-f2636edc915f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AsiaPacificMember_e57b21da-32b1-47aa-9334-f43a15c09d90" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_AsiaPacificMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_30b7140e-50c1-4ecf-b064-6610eb400fc9" xlink:to="loc_srt_AsiaPacificMember_e57b21da-32b1-47aa-9334-f43a15c09d90" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/OtherIncomeNetScheduleofOtherIncomeDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#OtherIncomeNetScheduleofOtherIncomeDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/OtherIncomeNetScheduleofOtherIncomeDetails" xlink:type="extended" id="i6788158369af4a48a4587a026b124d21_OtherIncomeNetScheduleofOtherIncomeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_daff546b-cd89-4a5b-992a-5c16dd66eb8a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnInterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstruments_6d2ee5fa-39a1-4c1e-9b9a-9ccfdc21c94f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GainLossOnInterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstruments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_daff546b-cd89-4a5b-992a-5c16dd66eb8a" xlink:to="loc_us-gaap_GainLossOnInterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstruments_6d2ee5fa-39a1-4c1e-9b9a-9ccfdc21c94f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_SaleOfInterestInPropertyPlantEquipmentPercent_23e82877-be3c-4c17-a441-3525ea2d3dc9" xlink:href="bsy-20220331.xsd#bsy_SaleOfInterestInPropertyPlantEquipmentPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_daff546b-cd89-4a5b-992a-5c16dd66eb8a" xlink:to="loc_bsy_SaleOfInterestInPropertyPlantEquipmentPercent_23e82877-be3c-4c17-a441-3525ea2d3dc9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_GainLossOnSaleOfInterestInPropertyPlantEquipment_c80341fe-50f5-45bc-9a20-5b11fba6ad9a" xlink:href="bsy-20220331.xsd#bsy_GainLossOnSaleOfInterestInPropertyPlantEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_daff546b-cd89-4a5b-992a-5c16dd66eb8a" xlink:to="loc_bsy_GainLossOnSaleOfInterestInPropertyPlantEquipment_c80341fe-50f5-45bc-9a20-5b11fba6ad9a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_c1fbca6c-8ebd-4bf0-a054-6c8c242acb2e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_daff546b-cd89-4a5b-992a-5c16dd66eb8a" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_c1fbca6c-8ebd-4bf0-a054-6c8c242acb2e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_9ab0026e-8153-4628-bbd6-2969deb33024" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_daff546b-cd89-4a5b-992a-5c16dd66eb8a" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_9ab0026e-8153-4628-bbd6-2969deb33024" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_602520b7-650a-4f33-8e5f-232677de9e46" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_9ab0026e-8153-4628-bbd6-2969deb33024" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_602520b7-650a-4f33-8e5f-232677de9e46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_602520b7-650a-4f33-8e5f-232677de9e46_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_602520b7-650a-4f33-8e5f-232677de9e46" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_602520b7-650a-4f33-8e5f-232677de9e46_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_3c68b16f-f9a1-4334-bc02-7c3724140745" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_602520b7-650a-4f33-8e5f-232677de9e46" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_3c68b16f-f9a1-4334-bc02-7c3724140745" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AirTransportationEquipmentMember_3ab1bda9-d695-4160-be18-0dd5e56a02c9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AirTransportationEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_3c68b16f-f9a1-4334-bc02-7c3724140745" xlink:to="loc_us-gaap_AirTransportationEquipmentMember_3ab1bda9-d695-4160-be18-0dd5e56a02c9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3dcc3245-eab7-4690-8400-a8ee941672cd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_9ab0026e-8153-4628-bbd6-2969deb33024" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3dcc3245-eab7-4690-8400-a8ee941672cd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_3dcc3245-eab7-4690-8400-a8ee941672cd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3dcc3245-eab7-4690-8400-a8ee941672cd" xlink:to="loc_us-gaap_RelatedPartyDomain_3dcc3245-eab7-4690-8400-a8ee941672cd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_44c4d52d-eb4a-4512-973a-a7921b6f264b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3dcc3245-eab7-4690-8400-a8ee941672cd" xlink:to="loc_us-gaap_RelatedPartyDomain_44c4d52d-eb4a-4512-973a-a7921b6f264b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_EntityControlledByCEOMember_6e917fed-5b69-43e2-b758-23adcf7baf27" xlink:href="bsy-20220331.xsd#bsy_EntityControlledByCEOMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_44c4d52d-eb4a-4512-973a-a7921b6f264b" xlink:to="loc_bsy_EntityControlledByCEOMember_6e917fed-5b69-43e2-b758-23adcf7baf27" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/NetIncomePerShareScheduleofBasicandDilutedNetIncomePerShareDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#NetIncomePerShareScheduleofBasicandDilutedNetIncomePerShareDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/NetIncomePerShareScheduleofBasicandDilutedNetIncomePerShareDetails" xlink:type="extended" id="i480236cf28864ea3a94de785abc96db4_NetIncomePerShareScheduleofBasicandDilutedNetIncomePerShareDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDilutedLineItems_3ebb4e12-499f-4eab-a2f1-511062457125" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareDilutedLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_NumeratorAbstract_b785e059-ff77-4a48-8332-1c46ae85b174" xlink:href="bsy-20220331.xsd#bsy_NumeratorAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedLineItems_3ebb4e12-499f-4eab-a2f1-511062457125" xlink:to="loc_bsy_NumeratorAbstract_b785e059-ff77-4a48-8332-1c46ae85b174" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_f3b906be-8a34-4499-997b-3dbea303ed2e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_NumeratorAbstract_b785e059-ff77-4a48-8332-1c46ae85b174" xlink:to="loc_us-gaap_NetIncomeLoss_f3b906be-8a34-4499-997b-3dbea303ed2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic_b66e9654-7ace-49bc-afc9-253bcc59f72b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_NumeratorAbstract_b785e059-ff77-4a48-8332-1c46ae85b174" xlink:to="loc_us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic_b66e9654-7ace-49bc-afc9-253bcc59f72b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_a7d7a7d4-4cdc-47bd-a242-1f7f458632af" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_NumeratorAbstract_b785e059-ff77-4a48-8332-1c46ae85b174" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_a7d7a7d4-4cdc-47bd-a242-1f7f458632af" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestOnConvertibleDebtNetOfTax_f93178a5-6435-41a3-805a-266f02ab9cdd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestOnConvertibleDebtNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_NumeratorAbstract_b785e059-ff77-4a48-8332-1c46ae85b174" xlink:to="loc_us-gaap_InterestOnConvertibleDebtNetOfTax_f93178a5-6435-41a3-805a-266f02ab9cdd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted_4246f081-1daf-4bdb-89f9-ebf4df77114b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_NumeratorAbstract_b785e059-ff77-4a48-8332-1c46ae85b174" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted_4246f081-1daf-4bdb-89f9-ebf4df77114b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_DenominatorAbstract_09c71b14-e3e5-4883-b95b-10719b91e447" xlink:href="bsy-20220331.xsd#bsy_DenominatorAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedLineItems_3ebb4e12-499f-4eab-a2f1-511062457125" xlink:to="loc_bsy_DenominatorAbstract_09c71b14-e3e5-4883-b95b-10719b91e447" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_e98a3f6d-c7ad-42ff-99f5-27437ab231b2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_DenominatorAbstract_09c71b14-e3e5-4883-b95b-10719b91e447" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_e98a3f6d-c7ad-42ff-99f5-27437ab231b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_34989514-3be6-48ec-90d7-d9e61fcd714f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_DenominatorAbstract_09c71b14-e3e5-4883-b95b-10719b91e447" xlink:to="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_34989514-3be6-48ec-90d7-d9e61fcd714f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_f63c0cfe-9051-4352-9b47-dcbe5e8b74a6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_DenominatorAbstract_09c71b14-e3e5-4883-b95b-10719b91e447" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_f63c0cfe-9051-4352-9b47-dcbe5e8b74a6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToConversionOfDebtSecurities_bcb3eba1-911f-45a9-82cd-c71574ce0dbb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncrementalCommonSharesAttributableToConversionOfDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_DenominatorAbstract_09c71b14-e3e5-4883-b95b-10719b91e447" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToConversionOfDebtSecurities_bcb3eba1-911f-45a9-82cd-c71574ce0dbb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_9bc4a7a8-7439-49d5-a86f-2c3acc5612a8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bsy_DenominatorAbstract_09c71b14-e3e5-4883-b95b-10719b91e447" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_9bc4a7a8-7439-49d5-a86f-2c3acc5612a8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_9489fc22-22a9-40c8-b469-0eae4acc60ac" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedLineItems_3ebb4e12-499f-4eab-a2f1-511062457125" xlink:to="loc_us-gaap_EarningsPerShareBasic_9489fc22-22a9-40c8-b469-0eae4acc60ac" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_c779fe34-d9b6-4fd7-bc5d-85c9ae1421b5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedLineItems_3ebb4e12-499f-4eab-a2f1-511062457125" xlink:to="loc_us-gaap_EarningsPerShareDiluted_c779fe34-d9b6-4fd7-bc5d-85c9ae1421b5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_ae791e75-d242-4208-8faa-439539f58039" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EarningsPerShareDilutedLineItems_3ebb4e12-499f-4eab-a2f1-511062457125" xlink:to="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_ae791e75-d242-4208-8faa-439539f58039" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_87b5e76a-6709-4699-9671-03d5d45377b9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_ae791e75-d242-4208-8faa-439539f58039" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_87b5e76a-6709-4699-9671-03d5d45377b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_87b5e76a-6709-4699-9671-03d5d45377b9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_87b5e76a-6709-4699-9671-03d5d45377b9" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_87b5e76a-6709-4699-9671-03d5d45377b9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_a87ddef6-be4d-4d0d-b417-abb9f6f1b006" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_87b5e76a-6709-4699-9671-03d5d45377b9" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_a87ddef6-be4d-4d0d-b417-abb9f6f1b006" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_0363be0c-7e0b-4be8-8c97-4ade8f89bf9d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_a87ddef6-be4d-4d0d-b417-abb9f6f1b006" xlink:to="loc_us-gaap_ConvertibleDebtMember_0363be0c-7e0b-4be8-8c97-4ade8f89bf9d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_0d5a100b-8dfa-455f-bbb2-19653b31fe0f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_ae791e75-d242-4208-8faa-439539f58039" xlink:to="loc_us-gaap_DebtInstrumentAxis_0d5a100b-8dfa-455f-bbb2-19653b31fe0f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_0d5a100b-8dfa-455f-bbb2-19653b31fe0f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_0d5a100b-8dfa-455f-bbb2-19653b31fe0f" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_0d5a100b-8dfa-455f-bbb2-19653b31fe0f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_62be0327-43dd-4d7e-883d-ebd5a7bb1bc5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_0d5a100b-8dfa-455f-bbb2-19653b31fe0f" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_62be0327-43dd-4d7e-883d-ebd5a7bb1bc5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_TwoThousandTwentySixNotesMember_f83bf6fa-11e8-4640-858c-6f2ec3daebfb" xlink:href="bsy-20220331.xsd#bsy_TwoThousandTwentySixNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_62be0327-43dd-4d7e-883d-ebd5a7bb1bc5" xlink:to="loc_bsy_TwoThousandTwentySixNotesMember_f83bf6fa-11e8-4640-858c-6f2ec3daebfb" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bentley.com/role/NetIncomePerShareScheduleofAntidilutiveSecuritiesExcludedfromComputationofEarningsPerShareDetails" xlink:type="simple" xlink:href="bsy-20220331.xsd#NetIncomePerShareScheduleofAntidilutiveSecuritiesExcludedfromComputationofEarningsPerShareDetails"/>
  <link:definitionLink xlink:role="http://www.bentley.com/role/NetIncomePerShareScheduleofAntidilutiveSecuritiesExcludedfromComputationofEarningsPerShareDetails" xlink:type="extended" id="i0a73fe7a85dc4a2a8df9fa191b0275b4_NetIncomePerShareScheduleofAntidilutiveSecuritiesExcludedfromComputationofEarningsPerShareDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c9cab82b-8fe1-4a19-8571-098b859875e6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_2ee9b61d-2e33-405b-bbbb-ca1898c12c2d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c9cab82b-8fe1-4a19-8571-098b859875e6" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_2ee9b61d-2e33-405b-bbbb-ca1898c12c2d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_0c45520c-09c3-4ad0-a5c4-068db047e18b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c9cab82b-8fe1-4a19-8571-098b859875e6" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_0c45520c-09c3-4ad0-a5c4-068db047e18b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_30d90c0a-5787-426a-83b7-0aef4df6fd76" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_0c45520c-09c3-4ad0-a5c4-068db047e18b" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_30d90c0a-5787-426a-83b7-0aef4df6fd76" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_30d90c0a-5787-426a-83b7-0aef4df6fd76_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_30d90c0a-5787-426a-83b7-0aef4df6fd76" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_30d90c0a-5787-426a-83b7-0aef4df6fd76_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_c908f4ed-d9d1-4d9d-bb6c-b16078e51e08" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_30d90c0a-5787-426a-83b7-0aef4df6fd76" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_c908f4ed-d9d1-4d9d-bb6c-b16078e51e08" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bsy_StockOptionsRestrictedStockAndRestrictedStockUnitsRSUsMember_069e330e-f687-415b-a8da-4275a42af66f" xlink:href="bsy-20220331.xsd#bsy_StockOptionsRestrictedStockAndRestrictedStockUnitsRSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_c908f4ed-d9d1-4d9d-bb6c-b16078e51e08" xlink:to="loc_bsy_StockOptionsRestrictedStockAndRestrictedStockUnitsRSUsMember_069e330e-f687-415b-a8da-4275a42af66f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-roles-2021-01-31.xsd#eedm"/>
  <link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
