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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019e8e01-7902-7825-98d9-b37172fd7103,g:58873d98-c630-41d8-8647-ac67b33000c2-->
<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.mongodb.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="simple" xlink:href="mdb-20260731.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS"/>
  <link:definitionLink xlink:role="http://www.mongodb.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e8e01-799d-7385-b56c-c1f7e2059958" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e8e01-799d-72cd-9522-6cf5f4bf9d8c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e8e01-799d-7385-b56c-c1f7e2059958" xlink:to="loc_us-gaap_StatementTable_019e8e01-799d-72cd-9522-6cf5f4bf9d8c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019e8e01-799d-7dbc-836f-c1e286081ae7" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e8e01-799d-72cd-9522-6cf5f4bf9d8c" xlink:to="loc_srt_ProductOrServiceAxis_019e8e01-799d-7dbc-836f-c1e286081ae7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e8e01-799d-7dbc-836f-c1e286081ae7_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019e8e01-799d-7dbc-836f-c1e286081ae7" xlink:to="loc_srt_ProductsAndServicesDomain_019e8e01-799d-7dbc-836f-c1e286081ae7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e8e01-799d-7ede-bbc6-5ba43a418cee" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019e8e01-799d-7dbc-836f-c1e286081ae7" xlink:to="loc_srt_ProductsAndServicesDomain_019e8e01-799d-7ede-bbc6-5ba43a418cee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LicenseMember_019e8e01-799d-773d-b6b2-96dd531503e3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LicenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e8e01-799d-7ede-bbc6-5ba43a418cee" xlink:to="loc_us-gaap_LicenseMember_019e8e01-799d-773d-b6b2-96dd531503e3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceMember_019e8e01-799d-7292-b36e-b25d5230b9ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e8e01-799d-7ede-bbc6-5ba43a418cee" xlink:to="loc_us-gaap_ServiceMember_019e8e01-799d-7292-b36e-b25d5230b9ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_019e8e01-799d-79ea-abc0-188164659f06" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e8e01-799d-7385-b56c-c1f7e2059958" xlink:to="loc_us-gaap_RevenuesAbstract_019e8e01-799d-79ea-abc0-188164659f06" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e8e01-799d-75fa-bca7-9379a337b968" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_019e8e01-799d-79ea-abc0-188164659f06" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e8e01-799d-75fa-bca7-9379a337b968" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenueAbstract_019e8e01-799d-7c03-8dd4-a0192d14dd4c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostOfRevenueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e8e01-799d-7385-b56c-c1f7e2059958" xlink:to="loc_us-gaap_CostOfRevenueAbstract_019e8e01-799d-7c03-8dd4-a0192d14dd4c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_019e8e01-799d-7cb4-9d0c-03fe0dd364ec" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostOfRevenueAbstract_019e8e01-799d-7c03-8dd4-a0192d14dd4c" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_019e8e01-799d-7cb4-9d0c-03fe0dd364ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_019e8e01-799d-7b12-beba-9cfeadad0f8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e8e01-799d-7385-b56c-c1f7e2059958" xlink:to="loc_us-gaap_GrossProfit_019e8e01-799d-7b12-beba-9cfeadad0f8e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_019e8e01-799d-7c74-817c-83606b1f6223" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e8e01-799d-7385-b56c-c1f7e2059958" xlink:to="loc_us-gaap_OperatingExpensesAbstract_019e8e01-799d-7c74-817c-83606b1f6223" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpense_019e8e01-799d-72f3-89a9-a1f0465160e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SellingAndMarketingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019e8e01-799d-7c74-817c-83606b1f6223" xlink:to="loc_us-gaap_SellingAndMarketingExpense_019e8e01-799d-72f3-89a9-a1f0465160e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_019e8e01-799d-76f7-a908-0394f291912a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019e8e01-799d-7c74-817c-83606b1f6223" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_019e8e01-799d-76f7-a908-0394f291912a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_019e8e01-799d-7552-8240-9e60ab57d4f4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019e8e01-799d-7c74-817c-83606b1f6223" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_019e8e01-799d-7552-8240-9e60ab57d4f4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_019e8e01-799d-73b0-9759-f5f65dca7678" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019e8e01-799d-7c74-817c-83606b1f6223" xlink:to="loc_us-gaap_OperatingExpenses_019e8e01-799d-73b0-9759-f5f65dca7678" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019e8e01-799d-744a-bf46-e4be838dff44" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e8e01-799d-7385-b56c-c1f7e2059958" xlink:to="loc_us-gaap_OperatingIncomeLoss_019e8e01-799d-744a-bf46-e4be838dff44" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_019e8e01-799d-73f0-ae6f-deadf95f9dfa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonoperatingIncomeExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e8e01-799d-7385-b56c-c1f7e2059958" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_019e8e01-799d-73f0-ae6f-deadf95f9dfa" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeNet_019e8e01-799d-792d-8052-3d2cac29922d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentIncomeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_019e8e01-799d-73f0-ae6f-deadf95f9dfa" xlink:to="loc_us-gaap_InvestmentIncomeNet_019e8e01-799d-792d-8052-3d2cac29922d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_019e8e01-799d-79ab-b540-61ff22d27d3b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_019e8e01-799d-73f0-ae6f-deadf95f9dfa" xlink:to="loc_us-gaap_InterestExpense_019e8e01-799d-79ab-b540-61ff22d27d3b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019e8e01-799d-7d6c-ab3d-4a9b7a9467a7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_019e8e01-799d-73f0-ae6f-deadf95f9dfa" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019e8e01-799d-7d6c-ab3d-4a9b7a9467a7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e8e01-799d-7915-85db-c0821631d1fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e8e01-799d-7385-b56c-c1f7e2059958" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e8e01-799d-7915-85db-c0821631d1fe" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019e8e01-799d-7a1d-bc97-1e5e7f86f8d9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e8e01-799d-7385-b56c-c1f7e2059958" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019e8e01-799d-7a1d-bc97-1e5e7f86f8d9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019e8e01-799d-7a86-ab24-66348d41780b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e8e01-799d-7385-b56c-c1f7e2059958" xlink:to="loc_us-gaap_NetIncomeLoss_019e8e01-799d-7a86-ab24-66348d41780b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_EarningsPerShareBasicAndDilutedEPSAbstract_019e8e01-799d-764a-9afe-8524e2579719" xlink:href="mdb-20260731.xsd#mdb_EarningsPerShareBasicAndDilutedEPSAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e8e01-799d-7385-b56c-c1f7e2059958" xlink:to="loc_mdb_EarningsPerShareBasicAndDilutedEPSAbstract_019e8e01-799d-764a-9afe-8524e2579719" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_019e8e01-799d-79b0-8077-faf6bdef0564" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mdb_EarningsPerShareBasicAndDilutedEPSAbstract_019e8e01-799d-764a-9afe-8524e2579719" xlink:to="loc_us-gaap_EarningsPerShareBasic_019e8e01-799d-79b0-8077-faf6bdef0564" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_019e8e01-799d-734b-b4d6-7ff8c14e6e7c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mdb_EarningsPerShareBasicAndDilutedEPSAbstract_019e8e01-799d-764a-9afe-8524e2579719" xlink:to="loc_us-gaap_EarningsPerShareDiluted_019e8e01-799d-734b-b4d6-7ff8c14e6e7c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_019e8e01-799d-7861-9953-ade737604a04" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e8e01-799d-7385-b56c-c1f7e2059958" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_019e8e01-799d-7861-9953-ade737604a04" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019e8e01-799d-7d43-a618-a2ea8525553b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_019e8e01-799d-7861-9953-ade737604a04" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019e8e01-799d-7d43-a618-a2ea8525553b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019e8e01-799d-70d7-8cc6-f99bb241db7e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_019e8e01-799d-7861-9953-ade737604a04" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019e8e01-799d-70d7-8cc6-f99bb241db7e" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mongodb.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="simple" xlink:href="mdb-20260731.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY"/>
  <link:definitionLink xlink:role="http://www.mongodb.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e8e01-799d-727c-9637-71518d91230f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e8e01-799d-7e20-a010-25c2213ca45c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e8e01-799d-727c-9637-71518d91230f" xlink:to="loc_us-gaap_StatementTable_019e8e01-799d-7e20-a010-25c2213ca45c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019e8e01-799d-7188-99cb-770ea2d0e014" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e8e01-799d-7e20-a010-25c2213ca45c" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019e8e01-799d-7188-99cb-770ea2d0e014" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e8e01-799d-7188-99cb-770ea2d0e014_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e8e01-799d-7188-99cb-770ea2d0e014" xlink:to="loc_us-gaap_EquityComponentDomain_019e8e01-799d-7188-99cb-770ea2d0e014_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e8e01-799d-7ae2-b72f-6af51b844419" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e8e01-799d-7188-99cb-770ea2d0e014" xlink:to="loc_us-gaap_EquityComponentDomain_019e8e01-799d-7ae2-b72f-6af51b844419" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019e8e01-799d-7dde-a1e1-0db4392a4fce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e8e01-799d-7ae2-b72f-6af51b844419" xlink:to="loc_us-gaap_CommonStockMember_019e8e01-799d-7dde-a1e1-0db4392a4fce" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019e8e01-799d-7f25-b8ea-26c1442d4ac2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e8e01-799d-7ae2-b72f-6af51b844419" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019e8e01-799d-7f25-b8ea-26c1442d4ac2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_019e8e01-799d-79d4-920b-100ad104f974" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e8e01-799d-7ae2-b72f-6af51b844419" xlink:to="loc_us-gaap_TreasuryStockCommonMember_019e8e01-799d-79d4-920b-100ad104f974" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e8e01-799d-7dff-8c8e-b8ebe38952e2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e8e01-799d-7ae2-b72f-6af51b844419" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e8e01-799d-7dff-8c8e-b8ebe38952e2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019e8e01-799d-7fe9-88d5-fa4354426021" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e8e01-799d-7ae2-b72f-6af51b844419" xlink:to="loc_us-gaap_RetainedEarningsMember_019e8e01-799d-7fe9-88d5-fa4354426021" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e8e01-799d-727c-9637-71518d91230f" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019e8e01-799d-77ab-a46a-07a782518129" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019e8e01-799d-77ab-a46a-07a782518129" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019e8e01-799d-7c89-9f7e-92f339b3fadf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_StockholdersEquity_019e8e01-799d-7c89-9f7e-92f339b3fadf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_019e8e01-799d-7c85-8595-d668d9f9cc4f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_019e8e01-799d-7c85-8595-d668d9f9cc4f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_019e8e01-799d-7c05-a5dd-4babeacc2ea2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_019e8e01-799d-7c05-a5dd-4babeacc2ea2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross_019e8e01-799d-7228-b037-30d7dad035fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross_019e8e01-799d-7228-b037-30d7dad035fe" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross_019e8e01-799d-792b-b9ad-d75d7b82e365" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross_019e8e01-799d-792b-b9ad-d75d7b82e365" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_StockIssuedDuringPeriodSharesPerformanceStockAwardGross_019e8e01-799d-7e9d-83d7-9a50e25db54e" xlink:href="mdb-20260731.xsd#mdb_StockIssuedDuringPeriodSharesPerformanceStockAwardGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_mdb_StockIssuedDuringPeriodSharesPerformanceStockAwardGross_019e8e01-799d-7e9d-83d7-9a50e25db54e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_019e8e01-799d-7b98-9b2b-b207fa652663" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_019e8e01-799d-7b98-9b2b-b207fa652663" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_019e8e01-799d-77e8-a0d4-8f7924bb6901" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_019e8e01-799d-77e8-a0d4-8f7924bb6901" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_StockIssuedDuringPeriodSharesAcquisitionsSubjectToFutureVesting_019e8e01-799d-7b5e-8719-256b68e901bf" xlink:href="mdb-20260731.xsd#mdb_StockIssuedDuringPeriodSharesAcquisitionsSubjectToFutureVesting"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_mdb_StockIssuedDuringPeriodSharesAcquisitionsSubjectToFutureVesting_019e8e01-799d-7b5e-8719-256b68e901bf" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_019e8e01-799d-7c0c-ad8d-d6fb6e491421" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_019e8e01-799d-7c0c-ad8d-d6fb6e491421" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_019e8e01-799d-7395-a644-271693f07ebe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_019e8e01-799d-7395-a644-271693f07ebe" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019e8e01-799d-71ec-9d44-c80670335750" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019e8e01-799d-71ec-9d44-c80670335750" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockRetiredCostMethodAmount_019e8e01-799d-7a79-878a-485a9fc2e136" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockRetiredCostMethodAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_TreasuryStockRetiredCostMethodAmount_019e8e01-799d-7a79-878a-485a9fc2e136" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_019e8e01-799d-7e8e-a861-f6b3204539ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_019e8e01-799d-7e8e-a861-f6b3204539ab" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019e8e01-799d-79ee-a403-20262728abad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019e8e01-799d-79ee-a403-20262728abad" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_01a03f18-5c5e-7c5a-a3c2-6f72172a4c3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_01a03f18-5c5e-7c5a-a3c2-6f72172a4c3e" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_01a03f18-5c5e-7811-8cc9-ad273a8dc9cc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_01a03f18-5c5e-7811-8cc9-ad273a8dc9cc" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax_019e8e01-799d-7ca1-8708-9f9c17e90a35" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax_019e8e01-799d-7ca1-8708-9f9c17e90a35" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent_019e8e01-799d-7e23-b21c-f69a77cb0b72" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent_019e8e01-799d-7e23-b21c-f69a77cb0b72" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019e8e01-799d-7e88-bde9-ae4314ddd388" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e8e01-799d-71d3-8f35-dc24aef42ef3" xlink:to="loc_us-gaap_NetIncomeLoss_019e8e01-799d-7e88-bde9-ae4314ddd388" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019e8e01-799d-734a-9d13-32e79357bee9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019e8e01-799d-7a50-9962-0a46c155e856" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mongodb.com/role/FairValueMeasurementsScheduleofFinancialAssetsandLiabilitiesDetails" xlink:type="simple" xlink:href="mdb-20260731.xsd#FairValueMeasurementsScheduleofFinancialAssetsandLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.mongodb.com/role/FairValueMeasurementsScheduleofFinancialAssetsandLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-784e-8239-d4f5af1b4d75" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e8e01-799d-7ae0-809e-c043fd66c767" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-784e-8239-d4f5af1b4d75" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e8e01-799d-7ae0-809e-c043fd66c767" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_019e8e01-799d-7cf5-9500-378fad9e0823" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e8e01-799d-7ae0-809e-c043fd66c767" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_019e8e01-799d-7cf5-9500-378fad9e0823" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019e8e01-799d-7cf5-9500-378fad9e0823_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_019e8e01-799d-7cf5-9500-378fad9e0823" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019e8e01-799d-7cf5-9500-378fad9e0823_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019e8e01-799d-7984-b448-686275f0dad0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_019e8e01-799d-7cf5-9500-378fad9e0823" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019e8e01-799d-7984-b448-686275f0dad0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_019e8e01-799d-734a-bb64-3bb6a03805bf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019e8e01-799d-7984-b448-686275f0dad0" xlink:to="loc_us-gaap_MoneyMarketFundsMember_019e8e01-799d-734a-bb64-3bb6a03805bf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e8e01-799d-7ba5-89a3-4f5e3fd10fda" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e8e01-799d-7ae0-809e-c043fd66c767" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e8e01-799d-7ba5-89a3-4f5e3fd10fda" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e8e01-799d-7ba5-89a3-4f5e3fd10fda_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e8e01-799d-7ba5-89a3-4f5e3fd10fda" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e8e01-799d-7ba5-89a3-4f5e3fd10fda_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e8e01-799d-7f45-b5ab-2e156909d722" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e8e01-799d-7ba5-89a3-4f5e3fd10fda" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e8e01-799d-7f45-b5ab-2e156909d722" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_019e8e01-799d-79e2-868b-8fdb47a967bc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e8e01-799d-7f45-b5ab-2e156909d722" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_019e8e01-799d-79e2-868b-8fdb47a967bc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e8e01-799d-7504-9ebb-37d48b24a0e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e8e01-799d-7ae0-809e-c043fd66c767" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e8e01-799d-7504-9ebb-37d48b24a0e4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e8e01-799d-7504-9ebb-37d48b24a0e4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e8e01-799d-7504-9ebb-37d48b24a0e4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e8e01-799d-7504-9ebb-37d48b24a0e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e8e01-799d-7221-9db5-239a34622062" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e8e01-799d-7504-9ebb-37d48b24a0e4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e8e01-799d-7221-9db5-239a34622062" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019e8e01-799d-7b27-8c4e-a0ea3a2d43c9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e8e01-799d-7221-9db5-239a34622062" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019e8e01-799d-7b27-8c4e-a0ea3a2d43c9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019e8e01-799d-7914-b2b5-23fb5fa13e09" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e8e01-799d-7221-9db5-239a34622062" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019e8e01-799d-7914-b2b5-23fb5fa13e09" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019e8e01-799d-7cd8-9c56-d77db01d3343" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e8e01-799d-7221-9db5-239a34622062" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019e8e01-799d-7cd8-9c56-d77db01d3343" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e8e01-799d-7e55-bd04-d36fdcd5ffb1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e8e01-799d-7ae0-809e-c043fd66c767" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e8e01-799d-7e55-bd04-d36fdcd5ffb1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e8e01-799d-7e55-bd04-d36fdcd5ffb1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e8e01-799d-7e55-bd04-d36fdcd5ffb1" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e8e01-799d-7e55-bd04-d36fdcd5ffb1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e8e01-799d-78a2-964a-9c21ee0470ee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e8e01-799d-7e55-bd04-d36fdcd5ffb1" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e8e01-799d-78a2-964a-9c21ee0470ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_019e8e01-799d-7b39-a858-b06ca7f3934b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e8e01-799d-78a2-964a-9c21ee0470ee" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_019e8e01-799d-7b39-a858-b06ca7f3934b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_019e8e01-799d-728e-bd65-4be69bf63834" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-784e-8239-d4f5af1b4d75" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_019e8e01-799d-728e-bd65-4be69bf63834" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAbstract_019e8e01-799d-7155-89c9-71b233224c15" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019e8e01-799d-728e-bd65-4be69bf63834" xlink:to="loc_us-gaap_CashAndCashEquivalentsAbstract_019e8e01-799d-7155-89c9-71b233224c15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019e8e01-799d-7472-826a-437d124ee1ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAbstract_019e8e01-799d-7155-89c9-71b233224c15" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019e8e01-799d-7472-826a-437d124ee1ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsAbstract_019e8e01-799d-78b1-9802-46ee4995d01a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShortTermInvestmentsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019e8e01-799d-728e-bd65-4be69bf63834" xlink:to="loc_us-gaap_ShortTermInvestmentsAbstract_019e8e01-799d-78b1-9802-46ee4995d01a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019e8e01-799d-7563-9afc-f8bb1253d128" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermInvestmentsAbstract_019e8e01-799d-78b1-9802-46ee4995d01a" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019e8e01-799d-7563-9afc-f8bb1253d128" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019e8e01-799d-7f20-bf3a-6e2e8db51d50" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019e8e01-799d-728e-bd65-4be69bf63834" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_019e8e01-799d-7f20-bf3a-6e2e8db51d50" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mongodb.com/role/FairValueMeasurementsMarketableSecuritiesDetails" xlink:type="simple" xlink:href="mdb-20260731.xsd#FairValueMeasurementsMarketableSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://www.mongodb.com/role/FairValueMeasurementsMarketableSecuritiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7f98-b733-0443d0807087" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e8e01-799d-76ce-9710-548c832eb234" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7f98-b733-0443d0807087" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e8e01-799d-76ce-9710-548c832eb234" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e8e01-799d-735a-be95-65b65cedcf75" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e8e01-799d-76ce-9710-548c832eb234" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e8e01-799d-735a-be95-65b65cedcf75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e8e01-799d-735a-be95-65b65cedcf75_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e8e01-799d-735a-be95-65b65cedcf75" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e8e01-799d-735a-be95-65b65cedcf75_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e8e01-799d-7a59-a8be-a32bec5ce585" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e8e01-799d-735a-be95-65b65cedcf75" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e8e01-799d-7a59-a8be-a32bec5ce585" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_019e8e01-799d-7c60-a7f4-15bfdea1492c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e8e01-799d-7a59-a8be-a32bec5ce585" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_019e8e01-799d-7c60-a7f4-15bfdea1492c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostCurrent_019e8e01-799d-7876-aab1-d8df84d962b0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7f98-b733-0443d0807087" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostCurrent_019e8e01-799d-7876-aab1-d8df84d962b0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostNoncurrent_019e8e01-799d-7f9c-a7e8-d53b9569888c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7f98-b733-0443d0807087" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostNoncurrent_019e8e01-799d-7f9c-a7e8-d53b9569888c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019e8e01-799d-7e2a-bdfa-7f0290f091b0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7f98-b733-0443d0807087" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019e8e01-799d-7e2a-bdfa-7f0290f091b0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_DebtSecuritiesAvailableForSaleUnrealizedGainLossCurrent_019e8e01-799d-706c-bd5e-05282889af16" xlink:href="mdb-20260731.xsd#mdb_DebtSecuritiesAvailableForSaleUnrealizedGainLossCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7f98-b733-0443d0807087" xlink:to="loc_mdb_DebtSecuritiesAvailableForSaleUnrealizedGainLossCurrent_019e8e01-799d-706c-bd5e-05282889af16" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_DebtSecuritiesAvailableForSaleUnrealizedGainLossNoncurrent_019e8e01-799d-7ba2-a708-48116231cdb4" xlink:href="mdb-20260731.xsd#mdb_DebtSecuritiesAvailableForSaleUnrealizedGainLossNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7f98-b733-0443d0807087" xlink:to="loc_mdb_DebtSecuritiesAvailableForSaleUnrealizedGainLossNoncurrent_019e8e01-799d-7ba2-a708-48116231cdb4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedGainLoss_019e8e01-799d-76b1-8f7c-0aebb6f1a57b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7f98-b733-0443d0807087" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedGainLoss_019e8e01-799d-76b1-8f7c-0aebb6f1a57b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesCurrent_019e8e01-799d-72f8-94cc-44e8d4472784" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecuritiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7f98-b733-0443d0807087" xlink:to="loc_us-gaap_MarketableSecuritiesCurrent_019e8e01-799d-72f8-94cc-44e8d4472784" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesNoncurrent_019e8e01-799d-78c1-87eb-eb3956527326" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecuritiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7f98-b733-0443d0807087" xlink:to="loc_us-gaap_MarketableSecuritiesNoncurrent_019e8e01-799d-78c1-87eb-eb3956527326" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecurities_019e8e01-799d-723e-b250-0d2a72fca5ae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7f98-b733-0443d0807087" xlink:to="loc_us-gaap_MarketableSecurities_019e8e01-799d-723e-b250-0d2a72fca5ae" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mongodb.com/role/FairValueMeasurementsAdditionalInformationDetails" xlink:type="simple" xlink:href="mdb-20260731.xsd#FairValueMeasurementsAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.mongodb.com/role/FairValueMeasurementsAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7d1f-a166-b96430ca89ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e8e01-799d-7839-8dc1-297046181d58" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7d1f-a166-b96430ca89ce" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e8e01-799d-7839-8dc1-297046181d58" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e8e01-799d-7ed5-8c2e-49187eb750e3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e8e01-799d-7839-8dc1-297046181d58" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e8e01-799d-7ed5-8c2e-49187eb750e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e8e01-799d-7ed5-8c2e-49187eb750e3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e8e01-799d-7ed5-8c2e-49187eb750e3" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e8e01-799d-7ed5-8c2e-49187eb750e3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e8e01-799d-7e8e-b8bf-3fcfac0605c0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e8e01-799d-7ed5-8c2e-49187eb750e3" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e8e01-799d-7e8e-b8bf-3fcfac0605c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_019e8e01-799d-7a62-a045-3962a03521cc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e8e01-799d-7e8e-b8bf-3fcfac0605c0" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_019e8e01-799d-7a62-a045-3962a03521cc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityOwnedNotReadilyMarketableAxis_019e8e01-799d-78cf-bdac-a0fc267363d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecurityOwnedNotReadilyMarketableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e8e01-799d-7839-8dc1-297046181d58" xlink:to="loc_us-gaap_SecurityOwnedNotReadilyMarketableAxis_019e8e01-799d-78cf-bdac-a0fc267363d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityOwnedNotReadilyMarketableNameDomain_019e8e01-799d-78cf-bdac-a0fc267363d4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecurityOwnedNotReadilyMarketableNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SecurityOwnedNotReadilyMarketableAxis_019e8e01-799d-78cf-bdac-a0fc267363d4" xlink:to="loc_us-gaap_SecurityOwnedNotReadilyMarketableNameDomain_019e8e01-799d-78cf-bdac-a0fc267363d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityOwnedNotReadilyMarketableNameDomain_019e8e01-799d-7e59-8899-5ea9001db528" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecurityOwnedNotReadilyMarketableNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SecurityOwnedNotReadilyMarketableAxis_019e8e01-799d-78cf-bdac-a0fc267363d4" xlink:to="loc_us-gaap_SecurityOwnedNotReadilyMarketableNameDomain_019e8e01-799d-7e59-8899-5ea9001db528" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_NonMarketableSecuritiesMember_019e8e01-799d-71e9-af26-2c00397326c7" xlink:href="mdb-20260731.xsd#mdb_NonMarketableSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedNotReadilyMarketableNameDomain_019e8e01-799d-7e59-8899-5ea9001db528" xlink:to="loc_mdb_NonMarketableSecuritiesMember_019e8e01-799d-71e9-af26-2c00397326c7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedGainLoss_019e8e01-799d-7f08-8fc3-9d9ac6b8853a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7d1f-a166-b96430ca89ce" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedGainLoss_019e8e01-799d-7f08-8fc3-9d9ac6b8853a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019e8e01-799d-760c-80a8-969629dca279" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7d1f-a166-b96430ca89ce" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019e8e01-799d-760c-80a8-969629dca279" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireInvestments_019e8e01-799d-7a5f-a196-506e41dba877" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7d1f-a166-b96430ca89ce" xlink:to="loc_us-gaap_PaymentsToAcquireInvestments_019e8e01-799d-7a5f-a196-506e41dba877" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnInvestments_019e8e01-799d-75ab-8562-ff6fe3e7c36d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrealizedGainLossOnInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7d1f-a166-b96430ca89ce" xlink:to="loc_us-gaap_UnrealizedGainLossOnInvestments_019e8e01-799d-75ab-8562-ff6fe3e7c36d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealizedInvestmentGainsLosses_019e8e01-799d-7993-85ee-c6ebd14b4d43" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealizedInvestmentGainsLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e8e01-799d-7d1f-a166-b96430ca89ce" xlink:to="loc_us-gaap_RealizedInvestmentGainsLosses_019e8e01-799d-7993-85ee-c6ebd14b4d43" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mongodb.com/role/GoodwillandAcquiredIntangibleAssetsNetScheduleofIntangibleAssetsDetails" xlink:type="simple" xlink:href="mdb-20260731.xsd#GoodwillandAcquiredIntangibleAssetsNetScheduleofIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.mongodb.com/role/GoodwillandAcquiredIntangibleAssetsNetScheduleofIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_019e8e01-799d-74b1-8918-22e48e597bf4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_019e8e01-799d-75df-885c-25d86867152c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_019e8e01-799d-74b1-8918-22e48e597bf4" xlink:to="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_019e8e01-799d-75df-885c-25d86867152c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019e8e01-799d-7488-b82e-a4a603ff0858" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_019e8e01-799d-75df-885c-25d86867152c" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019e8e01-799d-7488-b82e-a4a603ff0858" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e8e01-799d-7488-b82e-a4a603ff0858_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019e8e01-799d-7488-b82e-a4a603ff0858" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e8e01-799d-7488-b82e-a4a603ff0858_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e8e01-799d-72ef-85ea-f4bd99dd19be" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019e8e01-799d-7488-b82e-a4a603ff0858" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e8e01-799d-72ef-85ea-f4bd99dd19be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_019e8e01-799d-7298-8076-1fecdabdad87" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e8e01-799d-72ef-85ea-f4bd99dd19be" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_019e8e01-799d-7298-8076-1fecdabdad87" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternetDomainNamesMember_019e8e01-799d-7199-a47e-325c503e2232" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternetDomainNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e8e01-799d-72ef-85ea-f4bd99dd19be" xlink:to="loc_us-gaap_InternetDomainNamesMember_019e8e01-799d-7199-a47e-325c503e2232" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_01a03f15-20cf-7301-b4c6-9b142b39154d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e8e01-799d-72ef-85ea-f4bd99dd19be" xlink:to="loc_us-gaap_CustomerRelationshipsMember_01a03f15-20cf-7301-b4c6-9b142b39154d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019e8e01-799d-7015-affa-239e5c8110ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_019e8e01-799d-74b1-8918-22e48e597bf4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019e8e01-799d-7015-affa-239e5c8110ed" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019e8e01-799d-7409-aa36-d8734b6dcc47" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_019e8e01-799d-74b1-8918-22e48e597bf4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019e8e01-799d-7409-aa36-d8734b6dcc47" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019e8e01-799d-7d88-a21a-2c732eb56ad9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_019e8e01-799d-74b1-8918-22e48e597bf4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019e8e01-799d-7d88-a21a-2c732eb56ad9" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mongodb.com/role/BusinessCombinationsDetails" xlink:type="simple" xlink:href="mdb-20260731.xsd#BusinessCombinationsDetails"/>
  <link:definitionLink xlink:role="http://www.mongodb.com/role/BusinessCombinationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_019e8e01-799d-7375-a8b7-49f60aba3088" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019e8e01-799d-7d3e-a42f-1e9d81ad7bb6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019e8e01-799d-7375-a8b7-49f60aba3088" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019e8e01-799d-7d3e-a42f-1e9d81ad7bb6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019e8e01-799d-7673-88df-6a3d2b1d77ee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019e8e01-799d-7d3e-a42f-1e9d81ad7bb6" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019e8e01-799d-7673-88df-6a3d2b1d77ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e8e01-799d-7673-88df-6a3d2b1d77ee_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019e8e01-799d-7673-88df-6a3d2b1d77ee" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e8e01-799d-7673-88df-6a3d2b1d77ee_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e8e01-799d-7212-b604-9c8906112a35" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019e8e01-799d-7673-88df-6a3d2b1d77ee" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e8e01-799d-7212-b604-9c8906112a35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_ClarityBusinessHoldingsLLCMember_01a03eee-c48d-7183-8ad1-04fcaa87bb4f" xlink:href="mdb-20260731.xsd#mdb_ClarityBusinessHoldingsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e8e01-799d-7212-b604-9c8906112a35" xlink:to="loc_mdb_ClarityBusinessHoldingsLLCMember_01a03eee-c48d-7183-8ad1-04fcaa87bb4f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_01a03eee-c48d-7b6d-b11e-b14d52b5f268" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019e8e01-799d-7375-a8b7-49f60aba3088" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_01a03eee-c48d-7b6d-b11e-b14d52b5f268" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_01a03eef-b3e4-7adc-beea-49347b3d30cc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019e8e01-799d-7375-a8b7-49f60aba3088" xlink:to="loc_us-gaap_Goodwill_01a03eef-b3e4-7adc-beea-49347b3d30cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount_01a03ef0-9901-78d8-aeaf-d04ea4e2ba94" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019e8e01-799d-7375-a8b7-49f60aba3088" xlink:to="loc_us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount_01a03ef0-9901-78d8-aeaf-d04ea4e2ba94" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_01a03ef1-ffd3-70f2-979c-a83862dae277" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019e8e01-799d-7375-a8b7-49f60aba3088" xlink:to="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_01a03ef1-ffd3-70f2-979c-a83862dae277" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mongodb.com/role/LeasesAdditionalInformationDetails" xlink:type="simple" xlink:href="mdb-20260731.xsd#LeasesAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.mongodb.com/role/LeasesAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e8e01-7a3a-7cc8-ae41-9230844be56c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_019e8e01-7a3a-7641-87f4-c77bd06acd28" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e8e01-7a3a-7cc8-ae41-9230844be56c" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_019e8e01-7a3a-7641-87f4-c77bd06acd28" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019e8e01-7a3a-7d7b-af4c-039565033bc6" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_019e8e01-7a3a-7641-87f4-c77bd06acd28" xlink:to="loc_srt_RangeAxis_019e8e01-7a3a-7d7b-af4c-039565033bc6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e8e01-7a3a-7d7b-af4c-039565033bc6_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019e8e01-7a3a-7d7b-af4c-039565033bc6" xlink:to="loc_srt_RangeMember_019e8e01-7a3a-7d7b-af4c-039565033bc6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e8e01-7a3a-74ec-b7b5-8d3443a79b65" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019e8e01-7a3a-7d7b-af4c-039565033bc6" xlink:to="loc_srt_RangeMember_019e8e01-7a3a-74ec-b7b5-8d3443a79b65" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019e8e01-7a3a-7299-9c5a-91ffde5a8d20" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e8e01-7a3a-74ec-b7b5-8d3443a79b65" xlink:to="loc_srt_MinimumMember_019e8e01-7a3a-7299-9c5a-91ffde5a8d20" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019e8e01-7a3a-7f7a-949d-059b49d649a6" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e8e01-7a3a-74ec-b7b5-8d3443a79b65" xlink:to="loc_srt_MaximumMember_019e8e01-7a3a-7f7a-949d-059b49d649a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_LesseeLeaseTermOfContract_019e8e01-7a3a-7d35-9876-60b82b27e2b0" xlink:href="mdb-20260731.xsd#mdb_LesseeLeaseTermOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e8e01-7a3a-7cc8-ae41-9230844be56c" xlink:to="loc_mdb_LesseeLeaseTermOfContract_019e8e01-7a3a-7d35-9876-60b82b27e2b0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1_019e8e01-7a3a-70a9-b719-912dfaa23e79" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e8e01-7a3a-7cc8-ae41-9230844be56c" xlink:to="loc_us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1_019e8e01-7a3a-70a9-b719-912dfaa23e79" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount_019e8e01-7a3a-7f1e-b40a-e3a1aa5ace88" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e8e01-7a3a-7cc8-ae41-9230844be56c" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount_019e8e01-7a3a-7f1e-b40a-e3a1aa5ace88" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mongodb.com/role/RevenueScheduleoftotalrevenuebygeographicareasDetails" xlink:type="simple" xlink:href="mdb-20260731.xsd#RevenueScheduleoftotalrevenuebygeographicareasDetails"/>
  <link:definitionLink xlink:role="http://www.mongodb.com/role/RevenueScheduleoftotalrevenuebygeographicareasDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019e8e01-7a3b-77a4-acfa-873ed1f6fb5f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_019e8e01-7a3b-745d-91d1-d5f877e190ca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019e8e01-7a3b-77a4-acfa-873ed1f6fb5f" xlink:to="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_019e8e01-7a3b-745d-91d1-d5f877e190ca" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019e8e01-7a3b-780a-b540-bd7f50b79ca6" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_019e8e01-7a3b-745d-91d1-d5f877e190ca" xlink:to="loc_srt_StatementGeographicalAxis_019e8e01-7a3b-780a-b540-bd7f50b79ca6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019e8e01-7a3b-780a-b540-bd7f50b79ca6_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019e8e01-7a3b-780a-b540-bd7f50b79ca6" xlink:to="loc_srt_SegmentGeographicalDomain_019e8e01-7a3b-780a-b540-bd7f50b79ca6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019e8e01-7a3b-7ba8-8de4-0b212626460a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019e8e01-7a3b-780a-b540-bd7f50b79ca6" xlink:to="loc_srt_SegmentGeographicalDomain_019e8e01-7a3b-7ba8-8de4-0b212626460a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AmericasMember_019e8e01-7a3b-761a-a227-bec481a0438b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_AmericasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019e8e01-7a3b-7ba8-8de4-0b212626460a" xlink:to="loc_srt_AmericasMember_019e8e01-7a3b-761a-a227-bec481a0438b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EMEAMember_019e8e01-7a3b-70f7-9dc2-ff1120b07af6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EMEAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019e8e01-7a3b-7ba8-8de4-0b212626460a" xlink:to="loc_us-gaap_EMEAMember_019e8e01-7a3b-70f7-9dc2-ff1120b07af6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AsiaPacificMember_019e8e01-7a3b-736f-9771-465b467ad740" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_AsiaPacificMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019e8e01-7a3b-7ba8-8de4-0b212626460a" xlink:to="loc_srt_AsiaPacificMember_019e8e01-7a3b-736f-9771-465b467ad740" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019e8e01-7a3b-7b67-ab69-466f6f97e73d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_019e8e01-7a3b-745d-91d1-d5f877e190ca" xlink:to="loc_srt_ProductOrServiceAxis_019e8e01-7a3b-7b67-ab69-466f6f97e73d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-7b67-ab69-466f6f97e73d_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019e8e01-7a3b-7b67-ab69-466f6f97e73d" xlink:to="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-7b67-ab69-466f6f97e73d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-7175-8859-9bbe9be5a19a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019e8e01-7a3b-7b67-ab69-466f6f97e73d" xlink:to="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-7175-8859-9bbe9be5a19a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_MongoDBAtlasRelatedMember_019e8e01-7a3b-7b68-b3eb-432f32fb8d1f" xlink:href="mdb-20260731.xsd#mdb_MongoDBAtlasRelatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-7175-8859-9bbe9be5a19a" xlink:to="loc_mdb_MongoDBAtlasRelatedMember_019e8e01-7a3b-7b68-b3eb-432f32fb8d1f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_OtherSubscriptionMember_019e8e01-7a3b-72e9-84dd-412c253be690" xlink:href="mdb-20260731.xsd#mdb_OtherSubscriptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-7175-8859-9bbe9be5a19a" xlink:to="loc_mdb_OtherSubscriptionMember_019e8e01-7a3b-72e9-84dd-412c253be690" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceMember_019e8e01-7a3b-71a0-8f0a-4cb21b3828c4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-7175-8859-9bbe9be5a19a" xlink:to="loc_us-gaap_ServiceMember_019e8e01-7a3b-71a0-8f0a-4cb21b3828c4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e8e01-7a3b-7f12-80c9-d39f8b235257" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019e8e01-7a3b-77a4-acfa-873ed1f6fb5f" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e8e01-7a3b-7f12-80c9-d39f8b235257" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mongodb.com/role/RevenueAdditionalInformationDetails" xlink:type="simple" xlink:href="mdb-20260731.xsd#RevenueAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.mongodb.com/role/RevenueAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019e8e01-7a3b-7acb-a38c-c0acdd31765e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019e8e01-7a3b-7acb-a38c-c0acdd31765e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_019e8e01-7a3b-78ef-a1d7-e7cf0105e981" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019e8e01-7a3b-7acb-a38c-c0acdd31765e" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_019e8e01-7a3b-78ef-a1d7-e7cf0105e981" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019e8e01-7a3b-7170-846c-590621afe1cb" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019e8e01-7a3b-7acb-a38c-c0acdd31765e" xlink:to="loc_srt_RangeAxis_019e8e01-7a3b-7170-846c-590621afe1cb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e8e01-7a3b-7170-846c-590621afe1cb_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019e8e01-7a3b-7170-846c-590621afe1cb" xlink:to="loc_srt_RangeMember_019e8e01-7a3b-7170-846c-590621afe1cb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e8e01-7a3b-71d8-91de-1fc108c36aa9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019e8e01-7a3b-7170-846c-590621afe1cb" xlink:to="loc_srt_RangeMember_019e8e01-7a3b-71d8-91de-1fc108c36aa9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019e8e01-7a3b-735b-81a2-96e9ec2258b4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e8e01-7a3b-71d8-91de-1fc108c36aa9" xlink:to="loc_srt_MinimumMember_019e8e01-7a3b-735b-81a2-96e9ec2258b4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019e8e01-7a3b-7c2a-a90e-62c77ae6e35d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e8e01-7a3b-71d8-91de-1fc108c36aa9" xlink:to="loc_srt_MaximumMember_019e8e01-7a3b-7c2a-a90e-62c77ae6e35d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_019e8e01-7a3b-78b4-ad86-39b297ab24a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_ContractWithCustomerLiability_019e8e01-7a3b-78b4-ad86-39b297ab24a3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_ContractWithCustomerLiabilityRevenueRecognizedPercent_019e8e01-7a3b-76d7-bbb5-c16a0b8e86b7" xlink:href="mdb-20260731.xsd#mdb_ContractWithCustomerLiabilityRevenueRecognizedPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_mdb_ContractWithCustomerLiabilityRevenueRecognizedPercent_019e8e01-7a3b-76d7-bbb5-c16a0b8e86b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_019e8e01-7a3b-7d78-9055-197337be45e5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_019e8e01-7a3b-7d78-9055-197337be45e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_019e8e01-7a3b-7e13-81ca-5ba6dd590b63" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_019e8e01-7a3b-7e13-81ca-5ba6dd590b63" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019e8e01-7a3b-7fc0-98fb-6c29912ad9fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019e8e01-7a3b-7fc0-98fb-6c29912ad9fe" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNetCurrent_019e8e01-7a3b-7853-8250-f3a54db139f9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerAssetNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_ContractWithCustomerAssetNetCurrent_019e8e01-7a3b-7853-8250-f3a54db139f9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostNet_019e8e01-7a3b-7f5f-ac0b-02fbbbc2159d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CapitalizedContractCostNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_CapitalizedContractCostNet_019e8e01-7a3b-7f5f-ac0b-02fbbbc2159d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostNetNoncurrent_019e8e01-7a3b-78d0-82a5-953cba7f251f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CapitalizedContractCostNetNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_CapitalizedContractCostNetNoncurrent_019e8e01-7a3b-78d0-82a5-953cba7f251f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostAmortization_019e8e01-7a3b-74a6-922c-8079043baa26" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CapitalizedContractCostAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_CapitalizedContractCostAmortization_019e8e01-7a3b-74a6-922c-8079043baa26" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostImpairmentLoss_019e8e01-7a3b-7ebe-b376-34100db14f63" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CapitalizedContractCostImpairmentLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_CapitalizedContractCostImpairmentLoss_019e8e01-7a3b-7ebe-b376-34100db14f63" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mongodb.com/role/RevenueAdditionalInformationDetails_1" xlink:type="simple" xlink:href="mdb-20260731.xsd#RevenueAdditionalInformationDetails_1"/>
  <link:definitionLink xlink:role="http://www.mongodb.com/role/RevenueAdditionalInformationDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019e8e01-7a3b-7acb-a38c-c0acdd31765e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019e8e01-7a3b-7acb-a38c-c0acdd31765e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019e8e01-7a3b-7170-846c-590621afe1cb" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019e8e01-7a3b-7acb-a38c-c0acdd31765e" xlink:to="loc_srt_RangeAxis_019e8e01-7a3b-7170-846c-590621afe1cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e8e01-7a3b-7170-846c-590621afe1cb_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019e8e01-7a3b-7170-846c-590621afe1cb" xlink:to="loc_srt_RangeMember_019e8e01-7a3b-7170-846c-590621afe1cb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e8e01-7a3b-71d8-91de-1fc108c36aa9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019e8e01-7a3b-7170-846c-590621afe1cb" xlink:to="loc_srt_RangeMember_019e8e01-7a3b-71d8-91de-1fc108c36aa9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019e8e01-7a3b-735b-81a2-96e9ec2258b4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e8e01-7a3b-71d8-91de-1fc108c36aa9" xlink:to="loc_srt_MinimumMember_019e8e01-7a3b-735b-81a2-96e9ec2258b4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019e8e01-7a3b-7c2a-a90e-62c77ae6e35d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e8e01-7a3b-71d8-91de-1fc108c36aa9" xlink:to="loc_srt_MaximumMember_019e8e01-7a3b-7c2a-a90e-62c77ae6e35d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_019e8e01-7a3b-78b4-ad86-39b297ab24a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_ContractWithCustomerLiability_019e8e01-7a3b-78b4-ad86-39b297ab24a3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_ContractWithCustomerLiabilityRevenueRecognizedPercent_019e8e01-7a3b-76d7-bbb5-c16a0b8e86b7" xlink:href="mdb-20260731.xsd#mdb_ContractWithCustomerLiabilityRevenueRecognizedPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_mdb_ContractWithCustomerLiabilityRevenueRecognizedPercent_019e8e01-7a3b-76d7-bbb5-c16a0b8e86b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_019e8e01-7a3b-7d78-9055-197337be45e5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_019e8e01-7a3b-7d78-9055-197337be45e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_019e8e01-7a3b-7e13-81ca-5ba6dd590b63" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_019e8e01-7a3b-7e13-81ca-5ba6dd590b63" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019e8e01-7a3b-7fc0-98fb-6c29912ad9fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019e8e01-7a3b-7fc0-98fb-6c29912ad9fe" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNetCurrent_019e8e01-7a3b-7853-8250-f3a54db139f9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerAssetNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_ContractWithCustomerAssetNetCurrent_019e8e01-7a3b-7853-8250-f3a54db139f9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostNet_019e8e01-7a3b-7f5f-ac0b-02fbbbc2159d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CapitalizedContractCostNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_CapitalizedContractCostNet_019e8e01-7a3b-7f5f-ac0b-02fbbbc2159d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostNetNoncurrent_019e8e01-7a3b-78d0-82a5-953cba7f251f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CapitalizedContractCostNetNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_CapitalizedContractCostNetNoncurrent_019e8e01-7a3b-78d0-82a5-953cba7f251f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostAmortization_019e8e01-7a3b-74a6-922c-8079043baa26" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CapitalizedContractCostAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_CapitalizedContractCostAmortization_019e8e01-7a3b-74a6-922c-8079043baa26" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostImpairmentLoss_019e8e01-7a3b-7ebe-b376-34100db14f63" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CapitalizedContractCostImpairmentLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e8e01-7a3b-7f02-adeb-dcd21d634318" xlink:to="loc_us-gaap_CapitalizedContractCostImpairmentLoss_019e8e01-7a3b-7ebe-b376-34100db14f63" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mongodb.com/role/EquityScheduleofStockActivityDetails" xlink:type="simple" xlink:href="mdb-20260731.xsd#EquityScheduleofStockActivityDetails"/>
  <link:definitionLink xlink:role="http://www.mongodb.com/role/EquityScheduleofStockActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7710-a1e2-1430d72655d5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-7ea2-958e-584a06f8448d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7710-a1e2-1430d72655d5" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-7ea2-958e-584a06f8448d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019e8e01-7a3b-76ea-9e95-b3270583e0fa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-7ea2-958e-584a06f8448d" xlink:to="loc_us-gaap_AwardTypeAxis_019e8e01-7a3b-76ea-9e95-b3270583e0fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e8e01-7a3b-76ea-9e95-b3270583e0fa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019e8e01-7a3b-76ea-9e95-b3270583e0fa" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e8e01-7a3b-76ea-9e95-b3270583e0fa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e8e01-7a3b-77c5-be2f-e64efbb629a7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019e8e01-7a3b-76ea-9e95-b3270583e0fa" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e8e01-7a3b-77c5-be2f-e64efbb629a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019e8e01-7a3b-7262-b6ed-0dfb3e203aa4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e8e01-7a3b-77c5-be2f-e64efbb629a7" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019e8e01-7a3b-7262-b6ed-0dfb3e203aa4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_019e8e01-7a3b-7bb4-b8a8-dd94e71f7ba1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e8e01-7a3b-77c5-be2f-e64efbb629a7" xlink:to="loc_us-gaap_RestrictedStockMember_019e8e01-7a3b-7bb4-b8a8-dd94e71f7ba1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_019e8e01-7a3b-756d-b92a-0a3d047ea6ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e8e01-7a3b-77c5-be2f-e64efbb629a7" xlink:to="loc_us-gaap_PerformanceSharesMember_019e8e01-7a3b-756d-b92a-0a3d047ea6ed" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019e8e01-7a3b-72d9-b68a-82b63e4c219b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7710-a1e2-1430d72655d5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019e8e01-7a3b-72d9-b68a-82b63e4c219b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019e8e01-7a3b-708c-bea0-2a0b6339a1cc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019e8e01-7a3b-72d9-b68a-82b63e4c219b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019e8e01-7a3b-708c-bea0-2a0b6339a1cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019e8e01-7a3b-764f-bad4-cd3cc7f6d58c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019e8e01-7a3b-72d9-b68a-82b63e4c219b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019e8e01-7a3b-764f-bad4-cd3cc7f6d58c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019e8e01-7a3b-7a49-9d0c-263045eab032" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019e8e01-7a3b-72d9-b68a-82b63e4c219b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019e8e01-7a3b-7a49-9d0c-263045eab032" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPeriodIncreaseDecrease_019e8e01-7a3b-7570-88b5-dcceb7f73145" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPeriodIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019e8e01-7a3b-72d9-b68a-82b63e4c219b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPeriodIncreaseDecrease_019e8e01-7a3b-7570-88b5-dcceb7f73145" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_019e8e01-7a3b-7e57-a008-a71364ec72a4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019e8e01-7a3b-72d9-b68a-82b63e4c219b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_019e8e01-7a3b-7e57-a008-a71364ec72a4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019e8e01-7a3b-781e-b3c2-5b0ba9836225" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019e8e01-7a3b-70fb-96f1-7e28c1661c60" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7710-a1e2-1430d72655d5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019e8e01-7a3b-70fb-96f1-7e28c1661c60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019e8e01-7a3b-7f40-a417-779077636ba4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019e8e01-7a3b-70fb-96f1-7e28c1661c60" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019e8e01-7a3b-7f40-a417-779077636ba4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019e8e01-7a3b-7c33-b004-9466be37658d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019e8e01-7a3b-70fb-96f1-7e28c1661c60" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019e8e01-7a3b-7c33-b004-9466be37658d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019e8e01-7a3b-7461-944c-109cb8e2f15a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019e8e01-7a3b-70fb-96f1-7e28c1661c60" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019e8e01-7a3b-7461-944c-109cb8e2f15a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPeriodAdjustmentsWeightedAverageGrantDateFairValue_019e8e01-7a3b-7c86-b201-779d61cddfae" xlink:href="mdb-20260731.xsd#mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPeriodAdjustmentsWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019e8e01-7a3b-70fb-96f1-7e28c1661c60" xlink:to="loc_mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPeriodAdjustmentsWeightedAverageGrantDateFairValue_019e8e01-7a3b-7c86-b201-779d61cddfae" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_019e8e01-7a3b-783a-bbd1-8570e185eb3a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019e8e01-7a3b-70fb-96f1-7e28c1661c60" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_019e8e01-7a3b-783a-bbd1-8570e185eb3a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019e8e01-7a3b-7e1c-adba-dbb3096e356e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mongodb.com/role/EquityAdditionalInformationDetails" xlink:type="simple" xlink:href="mdb-20260731.xsd#EquityAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.mongodb.com/role/EquityAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7c9f-9530-08f98a12c934" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-761e-9693-1c58c9bca7b2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7c9f-9530-08f98a12c934" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-761e-9693-1c58c9bca7b2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019e8e01-7a3b-7251-b2ed-77b8add1bb6e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-761e-9693-1c58c9bca7b2" xlink:to="loc_us-gaap_AwardTypeAxis_019e8e01-7a3b-7251-b2ed-77b8add1bb6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e8e01-7a3b-7251-b2ed-77b8add1bb6e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019e8e01-7a3b-7251-b2ed-77b8add1bb6e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e8e01-7a3b-7251-b2ed-77b8add1bb6e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e8e01-7a3b-71d7-a03a-0fd8575c3c7d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019e8e01-7a3b-7251-b2ed-77b8add1bb6e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e8e01-7a3b-71d7-a03a-0fd8575c3c7d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_019e8e01-7a3b-751b-825d-b03b6eccfbeb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e8e01-7a3b-71d7-a03a-0fd8575c3c7d" xlink:to="loc_us-gaap_PerformanceSharesMember_019e8e01-7a3b-751b-825d-b03b6eccfbeb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_PerformanceSharesMarketConditionsMember_019e8e01-7a3b-76c5-9450-1ca464e01b49" xlink:href="mdb-20260731.xsd#mdb_PerformanceSharesMarketConditionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e8e01-7a3b-71d7-a03a-0fd8575c3c7d" xlink:to="loc_mdb_PerformanceSharesMarketConditionsMember_019e8e01-7a3b-76c5-9450-1ca464e01b49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_019e8e01-7a3b-7e6f-ac9a-6fc2684d95b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e8e01-7a3b-71d7-a03a-0fd8575c3c7d" xlink:to="loc_us-gaap_EmployeeStockMember_019e8e01-7a3b-7e6f-ac9a-6fc2684d95b6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019e8e01-7a3b-72e8-aeef-0c2cc623ee34" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-761e-9693-1c58c9bca7b2" xlink:to="loc_srt_RangeAxis_019e8e01-7a3b-72e8-aeef-0c2cc623ee34" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e8e01-7a3b-72e8-aeef-0c2cc623ee34_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019e8e01-7a3b-72e8-aeef-0c2cc623ee34" xlink:to="loc_srt_RangeMember_019e8e01-7a3b-72e8-aeef-0c2cc623ee34_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e8e01-7a3b-7f83-b347-d9b8ef8d403c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019e8e01-7a3b-72e8-aeef-0c2cc623ee34" xlink:to="loc_srt_RangeMember_019e8e01-7a3b-7f83-b347-d9b8ef8d403c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019e8e01-7a3b-7835-8b90-0f447ce0f596" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e8e01-7a3b-7f83-b347-d9b8ef8d403c" xlink:to="loc_srt_MinimumMember_019e8e01-7a3b-7835-8b90-0f447ce0f596" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019e8e01-7a3b-7588-b3f4-b8e75bd92eed" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e8e01-7a3b-7f83-b347-d9b8ef8d403c" xlink:to="loc_srt_MaximumMember_019e8e01-7a3b-7588-b3f4-b8e75bd92eed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_MarketConditionAchievementAxis_019e8e01-7a3b-73e0-b23d-57374cd1f82b" xlink:href="mdb-20260731.xsd#mdb_MarketConditionAchievementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-761e-9693-1c58c9bca7b2" xlink:to="loc_mdb_MarketConditionAchievementAxis_019e8e01-7a3b-73e0-b23d-57374cd1f82b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_MarketConditionAchievementDomain_019e8e01-7a3b-73e0-b23d-57374cd1f82b_default" xlink:href="mdb-20260731.xsd#mdb_MarketConditionAchievementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_mdb_MarketConditionAchievementAxis_019e8e01-7a3b-73e0-b23d-57374cd1f82b" xlink:to="loc_mdb_MarketConditionAchievementDomain_019e8e01-7a3b-73e0-b23d-57374cd1f82b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_MarketConditionAchievementDomain_019e8e01-7a3b-708e-917c-bc38b49fee30" xlink:href="mdb-20260731.xsd#mdb_MarketConditionAchievementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_mdb_MarketConditionAchievementAxis_019e8e01-7a3b-73e0-b23d-57374cd1f82b" xlink:to="loc_mdb_MarketConditionAchievementDomain_019e8e01-7a3b-708e-917c-bc38b49fee30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_MarketConditionOneMember_019e8e01-7a3b-7149-bb77-cd226f88a4d8" xlink:href="mdb-20260731.xsd#mdb_MarketConditionOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mdb_MarketConditionAchievementDomain_019e8e01-7a3b-708e-917c-bc38b49fee30" xlink:to="loc_mdb_MarketConditionOneMember_019e8e01-7a3b-7149-bb77-cd226f88a4d8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_MarketConditionTwoMember_019e8e01-7a3b-7556-a72c-5e4fd5717fd7" xlink:href="mdb-20260731.xsd#mdb_MarketConditionTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mdb_MarketConditionAchievementDomain_019e8e01-7a3b-708e-917c-bc38b49fee30" xlink:to="loc_mdb_MarketConditionTwoMember_019e8e01-7a3b-7556-a72c-5e4fd5717fd7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_MarketConditionThreeMember_019e8e01-7a3b-7623-aacc-9992b9e02ee4" xlink:href="mdb-20260731.xsd#mdb_MarketConditionThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mdb_MarketConditionAchievementDomain_019e8e01-7a3b-708e-917c-bc38b49fee30" xlink:to="loc_mdb_MarketConditionThreeMember_019e8e01-7a3b-7623-aacc-9992b9e02ee4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_MarketConditionFourMember_019e8e01-7a3b-727e-8410-336b12fef95e" xlink:href="mdb-20260731.xsd#mdb_MarketConditionFourMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mdb_MarketConditionAchievementDomain_019e8e01-7a3b-708e-917c-bc38b49fee30" xlink:to="loc_mdb_MarketConditionFourMember_019e8e01-7a3b-727e-8410-336b12fef95e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingAxis_019e8e01-7a3b-7846-89d4-06be8b4f6b03" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VestingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-761e-9693-1c58c9bca7b2" xlink:to="loc_us-gaap_VestingAxis_019e8e01-7a3b-7846-89d4-06be8b4f6b03" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_019e8e01-7a3b-7846-89d4-06be8b4f6b03_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_019e8e01-7a3b-7846-89d4-06be8b4f6b03" xlink:to="loc_us-gaap_VestingDomain_019e8e01-7a3b-7846-89d4-06be8b4f6b03_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_019e8e01-7a3b-70f1-a27e-419fcefffbf8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_019e8e01-7a3b-7846-89d4-06be8b4f6b03" xlink:to="loc_us-gaap_VestingDomain_019e8e01-7a3b-70f1-a27e-419fcefffbf8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_019e8e01-7a3b-7563-9c89-71f04b108efb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationAwardTrancheOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_019e8e01-7a3b-70f1-a27e-419fcefffbf8" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_019e8e01-7a3b-7563-9c89-71f04b108efb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_019e8e01-7a3b-7a54-8063-338fa6c7ed81" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationAwardTrancheTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_019e8e01-7a3b-70f1-a27e-419fcefffbf8" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_019e8e01-7a3b-7a54-8063-338fa6c7ed81" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheThreeMember_019e8e01-7a3b-7336-b3be-07399ca14352" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationAwardTrancheThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_019e8e01-7a3b-70f1-a27e-419fcefffbf8" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheThreeMember_019e8e01-7a3b-7336-b3be-07399ca14352" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_ShareBasedPaymentArrangementTrancheFourMember_019e8e01-7a3b-750e-85c8-8a2ad8be5201" xlink:href="mdb-20260731.xsd#mdb_ShareBasedPaymentArrangementTrancheFourMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_019e8e01-7a3b-70f1-a27e-419fcefffbf8" xlink:to="loc_mdb_ShareBasedPaymentArrangementTrancheFourMember_019e8e01-7a3b-750e-85c8-8a2ad8be5201" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramAxis_019e8e01-7a3b-7f08-8aa2-5990e8b343eb" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-761e-9693-1c58c9bca7b2" xlink:to="loc_srt_ShareRepurchaseProgramAxis_019e8e01-7a3b-7f08-8aa2-5990e8b343eb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_019e8e01-7a3b-7f08-8aa2-5990e8b343eb_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ShareRepurchaseProgramAxis_019e8e01-7a3b-7f08-8aa2-5990e8b343eb" xlink:to="loc_srt_ShareRepurchaseProgramDomain_019e8e01-7a3b-7f08-8aa2-5990e8b343eb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_019e8e01-7a3b-71fd-a4c2-27c06322ab82" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ShareRepurchaseProgramAxis_019e8e01-7a3b-7f08-8aa2-5990e8b343eb" xlink:to="loc_srt_ShareRepurchaseProgramDomain_019e8e01-7a3b-71fd-a4c2-27c06322ab82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_ShareRepurchaseProgramMember_019e8e01-7a3b-735c-a101-b3a85ab89c0b" xlink:href="mdb-20260731.xsd#mdb_ShareRepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramDomain_019e8e01-7a3b-71fd-a4c2-27c06322ab82" xlink:to="loc_mdb_ShareRepurchaseProgramMember_019e8e01-7a3b-735c-a101-b3a85ab89c0b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodFairValue_019e8e01-7a3b-7995-aa1a-43574ad3cc2f" xlink:href="mdb-20260731.xsd#mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7c9f-9530-08f98a12c934" xlink:to="loc_mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodFairValue_019e8e01-7a3b-7995-aa1a-43574ad3cc2f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestingPercentageOfTarget_019e8e01-7a3b-7c9e-93d6-15b881ca1136" xlink:href="mdb-20260731.xsd#mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestingPercentageOfTarget"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7c9f-9530-08f98a12c934" xlink:to="loc_mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestingPercentageOfTarget_019e8e01-7a3b-7c9e-93d6-15b881ca1136" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019e8e01-7a3b-7768-ba83-452387cc31fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7c9f-9530-08f98a12c934" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019e8e01-7a3b-7768-ba83-452387cc31fe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsThresholdConsecutiveTradingDays_019e8e01-7a3b-76a2-997e-d54e8fabc94d" xlink:href="mdb-20260731.xsd#mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsThresholdConsecutiveTradingDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7c9f-9530-08f98a12c934" xlink:to="loc_mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsThresholdConsecutiveTradingDays_019e8e01-7a3b-76a2-997e-d54e8fabc94d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsStockPriceTargetMinimum_019e8e01-7a3b-7471-b109-0b7dd0788dc1" xlink:href="mdb-20260731.xsd#mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsStockPriceTargetMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7c9f-9530-08f98a12c934" xlink:to="loc_mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsStockPriceTargetMinimum_019e8e01-7a3b-7471-b109-0b7dd0788dc1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsPerformanceFactor_019e8e01-7a3b-7841-9d9d-9b95d9545b4b" xlink:href="mdb-20260731.xsd#mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsPerformanceFactor"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7c9f-9530-08f98a12c934" xlink:to="loc_mdb_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsPerformanceFactor_019e8e01-7a3b-7841-9d9d-9b95d9545b4b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019e8e01-7a3b-7541-a581-d2e4f9d260a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7c9f-9530-08f98a12c934" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019e8e01-7a3b-7541-a581-d2e4f9d260a3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate_019e8e01-7a3b-7fac-bd99-d6c1b8a774b1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7c9f-9530-08f98a12c934" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate_019e8e01-7a3b-7fac-bd99-d6c1b8a774b1" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019e8e01-7a3b-7a03-84a2-bd5fe1e1d4ea" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7c9f-9530-08f98a12c934" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019e8e01-7a3b-7a03-84a2-bd5fe1e1d4ea" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_ShareRepurchaseProgramAuthorizedAdditionalAmount_019e8e01-7a3b-7614-968f-12546331e80d" xlink:href="mdb-20260731.xsd#mdb_ShareRepurchaseProgramAuthorizedAdditionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7c9f-9530-08f98a12c934" xlink:to="loc_mdb_ShareRepurchaseProgramAuthorizedAdditionalAmount_019e8e01-7a3b-7614-968f-12546331e80d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_019e8e01-7a3b-7bcd-bcbe-62500ece65f0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7c9f-9530-08f98a12c934" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_019e8e01-7a3b-7bcd-bcbe-62500ece65f0" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019e8e01-7a3b-7afe-b87a-418e542227ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7c9f-9530-08f98a12c934" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019e8e01-7a3b-7afe-b87a-418e542227ed" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019e8e01-7a3b-7330-9309-6ebb21f242c1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7c9f-9530-08f98a12c934" xlink:to="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019e8e01-7a3b-7330-9309-6ebb21f242c1" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019e8e01-7a3b-7b85-9a91-839a0077739c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7c9f-9530-08f98a12c934" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019e8e01-7a3b-7b85-9a91-839a0077739c" xlink:type="arc" order="13"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mongodb.com/role/EquityStockbasedCompensationExpenseRecognizedinStatementofOperationsDetails" xlink:type="simple" xlink:href="mdb-20260731.xsd#EquityStockbasedCompensationExpenseRecognizedinStatementofOperationsDetails"/>
  <link:definitionLink xlink:role="http://www.mongodb.com/role/EquityStockbasedCompensationExpenseRecognizedinStatementofOperationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7b10-a3ee-f57fd29794c9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-78ee-b0e3-200023d6683a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7b10-a3ee-f57fd29794c9" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-78ee-b0e3-200023d6683a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_019e8e01-7a3b-7275-b330-d89fa0b4a316" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementOfIncomeLocationBalanceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-78ee-b0e3-200023d6683a" xlink:to="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_019e8e01-7a3b-7275-b330-d89fa0b4a316" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019e8e01-7a3b-74ba-aa00-c2433a961507" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-78ee-b0e3-200023d6683a" xlink:to="loc_srt_ProductOrServiceAxis_019e8e01-7a3b-74ba-aa00-c2433a961507" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-74ba-aa00-c2433a961507_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019e8e01-7a3b-74ba-aa00-c2433a961507" xlink:to="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-74ba-aa00-c2433a961507_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-7d4e-8d03-eba04fc181c5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019e8e01-7a3b-74ba-aa00-c2433a961507" xlink:to="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-7d4e-8d03-eba04fc181c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LicenseMember_019e8e01-7a3b-77a8-aed2-0664d4e329d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LicenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-7d4e-8d03-eba04fc181c5" xlink:to="loc_us-gaap_LicenseMember_019e8e01-7a3b-77a8-aed2-0664d4e329d4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceMember_019e8e01-7a3b-7780-a140-718d5008fd5d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-7d4e-8d03-eba04fc181c5" xlink:to="loc_us-gaap_ServiceMember_019e8e01-7a3b-7780-a140-718d5008fd5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019e8e01-7a3b-70bf-a773-f6eb68f63090" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7b10-a3ee-f57fd29794c9" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019e8e01-7a3b-70bf-a773-f6eb68f63090" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mongodb.com/role/EquityStockbasedCompensationExpenseRecognizedinStatementofOperationsDetails_1" xlink:type="simple" xlink:href="mdb-20260731.xsd#EquityStockbasedCompensationExpenseRecognizedinStatementofOperationsDetails_1"/>
  <link:definitionLink xlink:role="http://www.mongodb.com/role/EquityStockbasedCompensationExpenseRecognizedinStatementofOperationsDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7b10-a3ee-f57fd29794c9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-78ee-b0e3-200023d6683a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7b10-a3ee-f57fd29794c9" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-78ee-b0e3-200023d6683a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019e8e01-7a3b-74ba-aa00-c2433a961507" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e8e01-7a3b-78ee-b0e3-200023d6683a" xlink:to="loc_srt_ProductOrServiceAxis_019e8e01-7a3b-74ba-aa00-c2433a961507" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-74ba-aa00-c2433a961507_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019e8e01-7a3b-74ba-aa00-c2433a961507" xlink:to="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-74ba-aa00-c2433a961507_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-7d4e-8d03-eba04fc181c5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019e8e01-7a3b-74ba-aa00-c2433a961507" xlink:to="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-7d4e-8d03-eba04fc181c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LicenseMember_019e8e01-7a3b-77a8-aed2-0664d4e329d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LicenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-7d4e-8d03-eba04fc181c5" xlink:to="loc_us-gaap_LicenseMember_019e8e01-7a3b-77a8-aed2-0664d4e329d4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceMember_019e8e01-7a3b-7780-a140-718d5008fd5d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e8e01-7a3b-7d4e-8d03-eba04fc181c5" xlink:to="loc_us-gaap_ServiceMember_019e8e01-7a3b-7780-a140-718d5008fd5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019e8e01-7a3b-70bf-a773-f6eb68f63090" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e8e01-7a3b-7b10-a3ee-f57fd29794c9" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019e8e01-7a3b-70bf-a773-f6eb68f63090" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mongodb.com/role/NetIncomeLossperShareScheduleofAntidilutiveSecuritiesExcludedfromtheComputationofDilutedNetLossperShareDetails" xlink:type="simple" xlink:href="mdb-20260731.xsd#NetIncomeLossperShareScheduleofAntidilutiveSecuritiesExcludedfromtheComputationofDilutedNetLossperShareDetails"/>
  <link:definitionLink xlink:role="http://www.mongodb.com/role/NetIncomeLossperShareScheduleofAntidilutiveSecuritiesExcludedfromtheComputationofDilutedNetLossperShareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019e8e01-7a3b-7d59-b852-14c6beadd0d1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019e8e01-7a3b-7aca-84ea-da8d702f114c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019e8e01-7a3b-7d59-b852-14c6beadd0d1" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019e8e01-7a3b-7aca-84ea-da8d702f114c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_019e8e01-7a3b-739c-9981-2e87da237a81" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019e8e01-7a3b-7aca-84ea-da8d702f114c" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_019e8e01-7a3b-739c-9981-2e87da237a81" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019e8e01-7a3b-739c-9981-2e87da237a81_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_019e8e01-7a3b-739c-9981-2e87da237a81" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019e8e01-7a3b-739c-9981-2e87da237a81_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019e8e01-7a3b-7fb3-aa52-4d336daf57e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_019e8e01-7a3b-739c-9981-2e87da237a81" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019e8e01-7a3b-7fb3-aa52-4d336daf57e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_019e8e01-7a3b-7490-8c9c-bb6cfba5691c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019e8e01-7a3b-7fb3-aa52-4d336daf57e7" xlink:to="loc_us-gaap_EmployeeStockOptionMember_019e8e01-7a3b-7490-8c9c-bb6cfba5691c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019e8e01-7a3b-7822-89b7-9d5d3837ea58" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019e8e01-7a3b-7fb3-aa52-4d336daf57e7" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019e8e01-7a3b-7822-89b7-9d5d3837ea58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_01a03ef7-7619-7d0d-9363-e6ec0fe829d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019e8e01-7a3b-7fb3-aa52-4d336daf57e7" xlink:to="loc_us-gaap_EmployeeStockMember_01a03ef7-7619-7d0d-9363-e6ec0fe829d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_019e8e01-7a3b-79c4-aabb-ca5a58bceb3d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019e8e01-7a3b-7fb3-aa52-4d336daf57e7" xlink:to="loc_us-gaap_RestrictedStockMember_019e8e01-7a3b-79c4-aabb-ca5a58bceb3d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_019e8e01-7a3b-79b7-b026-57f204f9e9c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019e8e01-7a3b-7fb3-aa52-4d336daf57e7" xlink:to="loc_us-gaap_PerformanceSharesMember_019e8e01-7a3b-79b7-b026-57f204f9e9c6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019ef24c-cc86-7bb1-bab2-5e23704c4a8b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019e8e01-7a3b-7aca-84ea-da8d702f114c" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019ef24c-cc86-7bb1-bab2-5e23704c4a8b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019ef24c-cc86-7bb1-bab2-5e23704c4a8b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019ef24c-cc86-7bb1-bab2-5e23704c4a8b" xlink:to="loc_us-gaap_ClassOfStockDomain_019ef24c-cc86-7bb1-bab2-5e23704c4a8b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019ef24c-cc86-7180-b76a-d2fac1377ca1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019ef24c-cc86-7bb1-bab2-5e23704c4a8b" xlink:to="loc_us-gaap_ClassOfStockDomain_019ef24c-cc86-7180-b76a-d2fac1377ca1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019ef24c-cc86-73e8-a746-85cf05823c1a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019ef24c-cc86-7180-b76a-d2fac1377ca1" xlink:to="loc_us-gaap_CommonClassAMember_019ef24c-cc86-73e8-a746-85cf05823c1a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_019e8e01-7a3b-7425-b18d-84b0f9d74df1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019e8e01-7a3b-7d59-b852-14c6beadd0d1" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_019e8e01-7a3b-7425-b18d-84b0f9d74df1" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd#IndividualsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd#ecd_AllIndividualsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_DwightMerrimanMember_01a03efe-7956-7e76-8676-56607af40e5c" xlink:href="mdb-20260731.xsd#mdb_DwightMerrimanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_mdb_DwightMerrimanMember_01a03efe-7956-7e76-8676-56607af40e5c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_CharlesHazardJr.Member_01a03efe-d4fc-7bb9-9dfb-642d762dc0b7" xlink:href="mdb-20260731.xsd#mdb_CharlesHazardJr.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_mdb_CharlesHazardJr.Member_01a03efe-d4fc-7bb9-9dfb-642d762dc0b7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mdb_ArchanaAgrawalMember_01a03eff-0f76-789c-a74a-d70f979019ca" xlink:href="mdb-20260731.xsd#mdb_ArchanaAgrawalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_mdb_ArchanaAgrawalMember_01a03eff-0f76-789c-a74a-d70f979019ca" xlink:type="arc" order="4"/>
  </link:definitionLink>
</link:linkbase>
