<?xml version="1.0" encoding="US-ASCII"?>
<!-- DFIN New ActiveDisclosure (SM) XBRL Schema Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date :2022-08-10T19:10:06.4491+00:00 -->
<!-- Copyright (c) 2022 Donnelly Financial Solutions, Inc. All Rights Reserved. -->
<xsd:schema targetNamespace="http://www.xometry.com/20220630" attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:country="http://xbrl.sec.gov/country/2022" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2020-01-21" xmlns:enum2="http://xbrl.org/2020/extensible-enumerations-2.0" xmlns:srt="http://fasb.org/srt/2022" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:us-gaap="http://fasb.org/us-gaap/2022" xmlns:dei="http://xbrl.sec.gov/dei/2022" xmlns:xmtr="http://www.xometry.com/20220630" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xlink="http://www.w3.org/1999/xlink">
  <xsd:import schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" namespace="http://www.xbrl.org/2003/instance"/>
  <xsd:import schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" namespace="http://www.xbrl.org/2003/linkbase"/>
  <xsd:import schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" namespace="http://xbrl.org/2005/xbrldt"/>
  <xsd:import schemaLocation="https://xbrl.sec.gov/dei/2022/dei-2022.xsd" namespace="http://xbrl.sec.gov/dei/2022"/>
  <xsd:import schemaLocation="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd" namespace="http://fasb.org/us-gaap/2022"/>
  <xsd:import schemaLocation="https://xbrl.sec.gov/country/2022/country-2022.xsd" namespace="http://xbrl.sec.gov/country/2022"/>
  <xsd:import schemaLocation="https://www.xbrl.org/dtr/type/2020-01-21/types.xsd" namespace="http://www.xbrl.org/dtr/type/2020-01-21"/>
  <xsd:import schemaLocation="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd" namespace="http://fasb.org/srt/2022"/>
  <xsd:annotation>
    <xsd:appinfo>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="xmtr-20220630_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:title="Labels link" xlink:type="simple"/>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="xmtr-20220630_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:title="Presentation link" xlink:type="simple"/>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="xmtr-20220630_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:title="Definition link" xlink:type="simple"/>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="xmtr-20220630_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:title="Calculation link" xlink:type="simple"/>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DocumentDocumentAndEntityInformation" id="Role_DocumentDocumentAndEntityInformation">
        <link:definition>100000 - Document - Document and Entity Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/StatementCondensedConsolidatedBalanceSheets1" id="StatementCondensedConsolidatedBalanceSheets1">
        <link:definition>100010 - Statement - Condensed Consolidated Balance Sheets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsParenthetical" id="StatementCondensedConsolidatedBalanceSheetsParenthetical">
        <link:definition>100020 - Statement - Condensed Consolidated Balance Sheets (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited2" id="StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited2">
        <link:definition>100030 - Statement - Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) 2</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited" id="Role_StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited">
        <link:definition>100040 - Statement - Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInConvertiblePreferredStockAndStockholdersEquityDeficitUnaudited" id="StatementCondensedConsolidatedStatementsOfChangesInConvertiblePreferredStockAndStockholdersEquityDeficitUnaudited">
        <link:definition>100050 - Statement - Condensed Consolidated Statements of Changes in Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited" id="Role_StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited">
        <link:definition>100060 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureOrganizationAndDescriptionOfBusiness" id="Role_DisclosureOrganizationAndDescriptionOfBusiness">
        <link:definition>100070 - Disclosure - Organization and Description of Business</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureBasisOfPresentationAndSummaryOfSignificantAccountingPolicies" id="Role_DisclosureBasisOfPresentationAndSummaryOfSignificantAccountingPolicies">
        <link:definition>100080 - Disclosure - Basis of Presentation and Summary of Significant Accounting Policies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureCreditConcentrations" id="Role_DisclosureCreditConcentrations">
        <link:definition>100090 - Disclosure - Credit Concentrations</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureInventory" id="Role_DisclosureInventory">
        <link:definition>100100 - Disclosure - Inventory</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosurePropertyAndEquipmentAndLongLivedAssets" id="Role_DisclosurePropertyAndEquipmentAndLongLivedAssets">
        <link:definition>100110 - Disclosure - Property and Equipment and Long-Lived Assets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureLeases" id="Role_DisclosureLeases">
        <link:definition>100120 - Disclosure - Leases</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureAcquisitions1" id="DisclosureAcquisitions1">
        <link:definition>100130 - Disclosure - Acquisitions</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureDisaggregatedRevenueInformation" id="DisclosureDisaggregatedRevenueInformation">
        <link:definition>100140 - Disclosure - Disaggregated Revenue Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureInvestmentInUnconsolidatedJointVenture1" id="DisclosureInvestmentInUnconsolidatedJointVenture1">
        <link:definition>100150 - Disclosure - Investment in Unconsolidated Joint Venture</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensation" id="Role_DisclosureStockBasedCompensation">
        <link:definition>100160 - Disclosure - Stock Based Compensation</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureIncomeTaxes" id="Role_DisclosureIncomeTaxes">
        <link:definition>100170 - Disclosure - Income Taxes</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureNetLossPerShareAttributableToCommonStockholders" id="Role_DisclosureNetLossPerShareAttributableToCommonStockholders">
        <link:definition>100180 - Disclosure - Net Loss Per Share Attributable to Common Stockholders</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureDebtCommitmentsAndContingencies" id="Role_DisclosureDebtCommitmentsAndContingencies">
        <link:definition>100190 - Disclosure - Debt Commitments and Contingencies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureSegments" id="Role_DisclosureSegments">
        <link:definition>100200 - Disclosure - Segments</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssets" id="Role_DisclosureGoodwillAndIntangibleAssets">
        <link:definition>100210 - Disclosure - Goodwill and Intangible Assets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureBasisOfPresentationAndSummaryOfSignificantAccountingPoliciesPolicies" id="Role_DisclosureBasisOfPresentationAndSummaryOfSignificantAccountingPoliciesPolicies">
        <link:definition>100220 - Disclosure - Basis of Presentation and Summary of Significant Accounting Policies (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureBasisOfPresentationAndSummaryOfSignificantAccountingPoliciesTables" id="Role_DisclosureBasisOfPresentationAndSummaryOfSignificantAccountingPoliciesTables">
        <link:definition>100230 - Disclosure - Basis of Presentation and Summary of Significant Accounting Policies (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureInventoryTables" id="Role_DisclosureInventoryTables">
        <link:definition>100240 - Disclosure - Inventory (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosurePropertyAndEquipmentAndLongLivedAssetsTables" id="Role_DisclosurePropertyAndEquipmentAndLongLivedAssetsTables">
        <link:definition>100250 - Disclosure - Property and Equipment and Long-Lived Assets (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureLeasesTables" id="Role_DisclosureLeasesTables">
        <link:definition>100260 - Disclosure - Leases (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureAcquisitionsTables" id="DisclosureAcquisitionsTables">
        <link:definition>100270 - Disclosure - Acquisitions (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureDisaggregatedRevenueInformationTables" id="DisclosureDisaggregatedRevenueInformationTables">
        <link:definition>100280 - Disclosure - Disaggregated Revenue Information (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensationTables" id="Role_DisclosureStockBasedCompensationTables">
        <link:definition>100290 - Disclosure - Stock Based Compensation (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureNetLossPerShareAttributableToCommonStockholdersTables" id="Role_DisclosureNetLossPerShareAttributableToCommonStockholdersTables">
        <link:definition>100300 - Disclosure - Net Loss Per Share Attributable to Common Stockholders (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureDebtCommitmentsAndContingenciesTables" id="DisclosureDebtCommitmentsAndContingenciesTables">
        <link:definition>100310 - Disclosure - Debt Commitments and Contingencies (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureSegmentsTables" id="Role_DisclosureSegmentsTables">
        <link:definition>100320 - Disclosure - Segments (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssetsTables" id="Role_DisclosureGoodwillAndIntangibleAssetsTables">
        <link:definition>100330 - Disclosure - Goodwill and Intangible Assets (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureOrganizationAndDescriptionOfBusinessAdditionalInformationDetails" id="Role_DisclosureOrganizationAndDescriptionOfBusinessAdditionalInformationDetails">
        <link:definition>100340 - Disclosure - Organization and Description of Business - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureBasisOfPresentationAndSummaryOfSignificantAccountingPoliciesAdditionalInformationDetails" id="DisclosureBasisOfPresentationAndSummaryOfSignificantAccountingPoliciesAdditionalInformationDetails">
        <link:definition>100350 - Disclosure - Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureBasisOfPresentationAndSummaryOfSignificantAccountingPoliciesSummaryOfContractLiabilitiesDetails" id="DisclosureBasisOfPresentationAndSummaryOfSignificantAccountingPoliciesSummaryOfContractLiabilitiesDetails">
        <link:definition>100360 - Disclosure - Basis of Presentation and Summary of Significant accounting Policies - Summary of Contract Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureCreditConcentrationsAdditionalInformationDetails" id="Role_DisclosureCreditConcentrationsAdditionalInformationDetails">
        <link:definition>100370 - Disclosure - Credit Concentrations - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureInventoryScheduleOfComponentsOfInventoryDetails" id="DisclosureInventoryScheduleOfComponentsOfInventoryDetails">
        <link:definition>100380 - Disclosure - Inventory - Schedule of Components of Inventory (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosurePropertyAndEquipmentAndLonglivedAssetsSummaryOfComponentsOfPropertyAndEquipmentDetails" id="DisclosurePropertyAndEquipmentAndLonglivedAssetsSummaryOfComponentsOfPropertyAndEquipmentDetails">
        <link:definition>100390 - Disclosure - Property and Equipment and Long-Lived Assets - Summary of Components of Property and Equipment (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosurePropertyAndEquipmentAndLonglivedAssetsAdditionalInformationDetails" id="DisclosurePropertyAndEquipmentAndLonglivedAssetsAdditionalInformationDetails">
        <link:definition>100400 - Disclosure - Property and Equipment and Long-Lived Assets - Additional Information - (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosurePropertyAndEquipmentAndLongLivedAssetsSummaryOfDepreciationExpenseDetails" id="Role_DisclosurePropertyAndEquipmentAndLongLivedAssetsSummaryOfDepreciationExpenseDetails">
        <link:definition>100410 - Disclosure - Property and Equipment and Long-Lived Assets - Summary of Depreciation Expense (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureLeasesScheduleOfOperatingLeaseExpenseDetails" id="Role_DisclosureLeasesScheduleOfOperatingLeaseExpenseDetails">
        <link:definition>100420 - Disclosure - Leases - Schedule of Operating Lease Expense (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureLeasesAdditionalInformationDetails" id="Role_DisclosureLeasesAdditionalInformationDetails">
        <link:definition>100430 - Disclosure - Leases - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureAcquisitionsAdditionalInformationDetails" id="DisclosureAcquisitionsAdditionalInformationDetails">
        <link:definition>100440 - Disclosure - Acquisitions - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureAcquisitionsSummaryOfConsiderationPaidAndPreliminaryFairValueOfAssetsAcquiredAndLiabilitiesAssumedDetails" id="DisclosureAcquisitionsSummaryOfConsiderationPaidAndPreliminaryFairValueOfAssetsAcquiredAndLiabilitiesAssumedDetails">
        <link:definition>100450 - Disclosure - Acquisitions - Summary of Consideration Paid and Preliminary Fair Value of Assets Acquired and Liabilities Assumed (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureAcquisitionsSummaryOfFairValueOfIdentifiableIntangibleAssetsDetails" id="DisclosureAcquisitionsSummaryOfFairValueOfIdentifiableIntangibleAssetsDetails">
        <link:definition>100460 - Disclosure - Acquisitions - Summary of Fair Value of Identifiable Intangible Assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureAcquisitionsScheduleOfUnauditedProFormaCondensedCombinedFinancialInformationDetails" id="DisclosureAcquisitionsScheduleOfUnauditedProFormaCondensedCombinedFinancialInformationDetails">
        <link:definition>100470 - Disclosure - Acquisitions - Schedule of Unaudited Pro Forma Condensed Combined Financial Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureDisaggregatedRevenueInformationScheduleOfDisaggregatedRevenueInformationDetails" id="DisclosureDisaggregatedRevenueInformationScheduleOfDisaggregatedRevenueInformationDetails">
        <link:definition>100480 - Disclosure - Disaggregated Revenue Information - Schedule of Disaggregated Revenue Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureInvestmentInUnconsolidatedJointVentureAdditionalInformationDetails" id="DisclosureInvestmentInUnconsolidatedJointVentureAdditionalInformationDetails">
        <link:definition>100490 - Disclosure - Investment in Unconsolidated Joint Venture - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensationAdditionalInformationDetails" id="Role_DisclosureStockBasedCompensationAdditionalInformationDetails">
        <link:definition>100500 - Disclosure - Stock Based Compensation - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensationScheduleOfWeightedAverageAssumptionsDetails" id="Role_DisclosureStockBasedCompensationScheduleOfWeightedAverageAssumptionsDetails">
        <link:definition>100510 - Disclosure - Stock Based Compensation - Schedule of Weighted Average Assumptions (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensationSummaryOfStockOptionActivityDetails" id="Role_DisclosureStockBasedCompensationSummaryOfStockOptionActivityDetails">
        <link:definition>100520 - Disclosure - Stock Based Compensation - Summary of Stock Option Activity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureStockBasedCompensationSummaryOfRestrictedStockUnitActivityDetails" id="DisclosureStockBasedCompensationSummaryOfRestrictedStockUnitActivityDetails">
        <link:definition>100530 - Disclosure - Stock Based Compensation - Summary of Restricted Stock Unit Activity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureStockBasedCompensationScheduleOfTotalStockbasedCompensationCostsDetails" id="DisclosureStockBasedCompensationScheduleOfTotalStockbasedCompensationCostsDetails">
        <link:definition>100540 - Disclosure - Stock Based Compensation - Schedule of Total Stock-based Compensation Costs (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureIncomeTaxesAdditionalInformationDetails" id="Role_DisclosureIncomeTaxesAdditionalInformationDetails">
        <link:definition>100550 - Disclosure - Income Taxes - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureNetLossPerShareAttributableToCommonStockholdersComputationOfBasicAndDilutedNetLossPerShareAttributableToCommonStockholdersDetails" id="Role_DisclosureNetLossPerShareAttributableToCommonStockholdersComputationOfBasicAndDilutedNetLossPerShareAttributableToCommonStockholdersDetails">
        <link:definition>100560 - Disclosure - Net Loss Per Share Attributable to Common Stockholders - Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureNetLossPerShareAttributableToCommonStockholdersScheduleOfOutstandingSharesOfPotentiallyDilutiveSecuritiesExcludedFromComputation" id="DisclosureNetLossPerShareAttributableToCommonStockholdersScheduleOfOutstandingSharesOfPotentiallyDilutiveSecuritiesExcludedFromComputation">
        <link:definition>100570 - Disclosure - Net Loss Per Share Attributable to Common Stockholders - Schedule of Outstanding Shares of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureDebtCommitmentsAndContingenciesAdditionalInformationDetails" id="Role_DisclosureDebtCommitmentsAndContingenciesAdditionalInformationDetails">
        <link:definition>100580 - Disclosure - Debt Commitments and Contingencies - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureDebtCommitmentsAndContingenciesScheduleOfOutstandingPrincipalAmountAndCarryingValueOfNotesDetails" id="DisclosureDebtCommitmentsAndContingenciesScheduleOfOutstandingPrincipalAmountAndCarryingValueOfNotesDetails">
        <link:definition>100590 - Disclosure - Debt Commitments and Contingencies - Schedule of Outstanding Principal Amount and Carrying Value of Notes (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureDebtCommitmentsAndContingenciesScheduleOfInterestExpenseRelatedToNotesDetails" id="DisclosureDebtCommitmentsAndContingenciesScheduleOfInterestExpenseRelatedToNotesDetails">
        <link:definition>100600 - Disclosure - Debt Commitments and Contingencies - Schedule of Interest Expense Related to Notes (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureDebtCommitmentsAndContingenciesScheduleOfCarryingValueAndEstimatedFairValueOfNotesDetails" id="DisclosureDebtCommitmentsAndContingenciesScheduleOfCarryingValueAndEstimatedFairValueOfNotesDetails">
        <link:definition>100610 - Disclosure - Debt Commitments and Contingencies - Schedule of Carrying Value and Estimated Fair Value of Notes (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureSegmentsAdditionalInformationDetails" id="Role_DisclosureSegmentsAdditionalInformationDetails">
        <link:definition>100620 - Disclosure - Segments - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureSegmentsSummaryOfSegmentInformationDetails" id="Role_DisclosureSegmentsSummaryOfSegmentInformationDetails">
        <link:definition>100630 - Disclosure - Segments - Summary of Segment Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssetsSummaryOfIntangibleAssetsDetails" id="Role_DisclosureGoodwillAndIntangibleAssetsSummaryOfIntangibleAssetsDetails">
        <link:definition>100640 - Disclosure - Goodwill and Intangible Assets - Summary of Intangible Assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsScheduleOfCarryingAmountOfGoodwillDetails" id="DisclosureGoodwillAndIntangibleAssetsScheduleOfCarryingAmountOfGoodwillDetails">
        <link:definition>100650 - Disclosure - Goodwill and Intangible Assets - Schedule of Carrying Amount of Goodwill (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssetsAdditionalInformationDetails" id="Role_DisclosureGoodwillAndIntangibleAssetsAdditionalInformationDetails">
        <link:definition>100660 - Disclosure - Goodwill and Intangible Assets - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.xometry.com/20220630/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssetsScheduleOfAmortizationExpenseDetails" id="Role_DisclosureGoodwillAndIntangibleAssetsScheduleOfAmortizationExpenseDetails">
        <link:definition>100670 - Disclosure - Goodwill and Intangible Assets - Schedule of Amortization Expense (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
    </xsd:appinfo>
  </xsd:annotation>
  <xsd:element id="xmtr_BasisOfPresentationAndSummaryOfSignificantAccountingPoliciesAbstract" name="BasisOfPresentationAndSummaryOfSignificantAccountingPoliciesAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_NoncashFinancingItemsAbstract" name="NoncashFinancingItemsAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_NoncashInvestingItemsAbstract" name="NoncashInvestingItemsAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_AggregateNonContingentPortionOfPurchasePrice" name="AggregateNonContingentPortionOfPurchasePrice" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="xmtr_AmortizationExpenseIncomeOfDeferredSalesCommission" name="AmortizationExpenseIncomeOfDeferredSalesCommission" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="xmtr_BenefitRelatedToAdjustmentsInFairValueOfAssets" name="BenefitRelatedToAdjustmentsInFairValueOfAssets" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="xmtr_BusinessAcquisitionProFormaNetIncomeLossAvailableToCommonStockholders" name="BusinessAcquisitionProFormaNetIncomeLossAvailableToCommonStockholders" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="xmtr_BusinessCombinationChangesToInitialPurchasePriceAllocation" name="BusinessCombinationChangesToInitialPurchasePriceAllocation" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="xmtr_BusinessCombinationFairValueOfContingentConsideration" name="BusinessCombinationFairValueOfContingentConsideration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="xmtr_BusinessCombinationInitialFairValueOfContingentConsideration" name="BusinessCombinationInitialFairValueOfContingentConsideration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="xmtr_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractLiabilities" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="xmtr_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIncomeTaxesPayable" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIncomeTaxesPayable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="xmtr_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInvestmentInUnconsolidatedJointVenture" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInvestmentInUnconsolidatedJointVenture" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="xmtr_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRightOfUseAsset" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRightOfUseAsset" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="xmtr_CapitalizedContractCostAmortizationPeriodOverContractRenewal" name="CapitalizedContractCostAmortizationPeriodOverContractRenewal" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_ContractWithCustomerLiabilityNoncurrentPaymentsReceivedInAdvance" name="ContractWithCustomerLiabilityNoncurrentPaymentsReceivedInAdvance" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="xmtr_ContractWithCustomerLiabilityRevenueRecognizedCurrent" name="ContractWithCustomerLiabilityRevenueRecognizedCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="xmtr_CouponInterestExpenseDebt" name="CouponInterestExpenseDebt" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="xmtr_DebtInstrumentIndentureDate" name="DebtInstrumentIndentureDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_DonationOfCommonStock" name="DonationOfCommonStock" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="xmtr_EntityIncorporationMonthAndYearOfIncorporation" name="EntityIncorporationMonthAndYearOfIncorporation" type="xbrli:gYearMonthItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_IncomeLossFromUnconsolidatedJointVenture" name="IncomeLossFromUnconsolidatedJointVenture" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="xmtr_IncreaseDecreaseInLeaseLiabilities" name="IncreaseDecreaseInLeaseLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="xmtr_InventoryTools" name="InventoryTools" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="xmtr_MinimumNumberOfSuppliersAvailableInIndustrialBuyingEngineOnThomasnetCom" name="MinimumNumberOfSuppliersAvailableInIndustrialBuyingEngineOnThomasnetCom" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_NonCashAmountsIncurredInConnectionWithInitialPublicOffering" name="NonCashAmountsIncurredInConnectionWithInitialPublicOffering" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="xmtr_NonCashIncomeTaxExpenseBenefit" name="NonCashIncomeTaxExpenseBenefit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="xmtr_NumberOfBusinessDay" name="NumberOfBusinessDay" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_NumberOfCustomer" name="NumberOfCustomer" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_NumberOfNewLeases" name="NumberOfNewLeases" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_OperationsAndSupportExpense" name="OperationsAndSupportExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="xmtr_PercentageOfSalesPriceAndApplicableConversionRate" name="PercentageOfSalesPriceAndApplicableConversionRate" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_ProvisionForEstimatedReturnsRefundsOrAllowances" name="ProvisionForEstimatedReturnsRefundsOrAllowances" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="xmtr_RemainingNetOperatingLossCarryforwards" name="RemainingNetOperatingLossCarryforwards" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="xmtr_ReversalOfExpenseRelatedToAdjustmentsInFairValueOfAssets" name="ReversalOfExpenseRelatedToAdjustmentsInFairValueOfAssets" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="xmtr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTermExercised" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTermExercised" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTermGranted" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTermGranted" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanTerminationMonthAndYear" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanTerminationMonthAndYear" type="xbrli:gYearMonthItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_StockIssuedDuringPeriodSharesDonatedCommonStock" name="StockIssuedDuringPeriodSharesDonatedCommonStock" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_StockIssuedDuringPeriodValueDonatedCommonStock" name="StockIssuedDuringPeriodValueDonatedCommonStock" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="xmtr_WarrantsAgreementExpirationDate" name="WarrantsAgreementExpirationDate" type="xbrli:gYearMonthItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_DisclosureIncomeTaxesAdditionalInformationDetailsLineItems" name="DisclosureIncomeTaxesAdditionalInformationDetailsLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_GoodwillAndIntangibleAssetsLineItems" name="GoodwillAndIntangibleAssetsLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_AmendedAndRestatedLoanAndSecurityAgreementMember" name="AmendedAndRestatedLoanAndSecurityAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_BigBlueSawLlcMember" name="BigBlueSawLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_ConvertibleNotesMember" name="ConvertibleNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_ConvertiblePreferredStocksSeedOneSeedTwoSeriesAOneSeriesATwoSeriesBSeriesCSeriesDSeriesEMember" name="ConvertiblePreferredStocksSeedOneSeedTwoSeriesAOneSeriesATwoSeriesBSeriesCSeriesDSeriesEMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_ExistingCustomersMember" name="ExistingCustomersMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_FactoryFourMember" name="FactoryFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_HerculesCapitalIncMember" name="HerculesCapitalIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_IncomCoLimitedMember" name="IncomCoLimitedMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_IndustrialMediaLimitedLiabilityCorporationMember" name="IndustrialMediaLimitedLiabilityCorporationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_LeaseIntangibleAssetsMember" name="LeaseIntangibleAssetsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_MarketplaceRevenueMember" name="MarketplaceRevenueMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_NewCustomersMember" name="NewCustomersMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_NewLeaseForOfficeInNorthBethesdaMember" name="NewLeaseForOfficeInNorthBethesdaMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_OperationsAndSupportMember" name="OperationsAndSupportMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_ProductDevelopmentMember" name="ProductDevelopmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_RichMediaGroupLimitedLiabilityCorporationsMember" name="RichMediaGroupLimitedLiabilityCorporationsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_SalesContractAcquisitionCostsMember" name="SalesContractAcquisitionCostsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_SeriesBConvertiblePreferredStockMember" name="SeriesBConvertiblePreferredStockMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_SharesReservedForCharitableContributionMember" name="SharesReservedForCharitableContributionMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_SupplierServiceRevenueMember" name="SupplierServiceRevenueMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_TermLoanIfRepaidPriorToNovemberOneTwentyTwentyOneMember" name="TermLoanIfRepaidPriorToNovemberOneTwentyTwentyOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_TermLoanMember" name="TermLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_ThomasPublishingCompanyMember" name="ThomasPublishingCompanyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_TwoNewOfficeLeasesMember" name="TwoNewOfficeLeasesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_TwoThousandFourteenEquityIncentivePlanMember" name="TwoThousandFourteenEquityIncentivePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_TwoThousandSixteenEquityIncentivePlanMember" name="TwoThousandSixteenEquityIncentivePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_TwoThousandTwentyOneEquityIncentivePlanMember" name="TwoThousandTwentyOneEquityIncentivePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_TwoThousandTwentySevenConvertibleSeniorNotesMember" name="TwoThousandTwentySevenConvertibleSeniorNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_UnvestedRestrictedStockUnitsMember" name="UnvestedRestrictedStockUnitsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_VendorRelationshipsMember" name="VendorRelationshipsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_GoodwillAndIntangibleAssetsTable" name="GoodwillAndIntangibleAssetsTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_IncomeTaxesTable" name="IncomeTaxesTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="xmtr_GeneralAndAdministrativePolicyTextBlock" name="GeneralAndAdministrativePolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_OperationsAndSupportPolicyTextBlock" name="OperationsAndSupportPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_ScheduleOfDebtInstrumentsInterestExpenseTableTextBlock" name="ScheduleOfDebtInstrumentsInterestExpenseTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_ScheduleOfDepreciationExpensesTableTextBlock" name="ScheduleOfDepreciationExpensesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="xmtr_ScheduleOfOperatingLeaseExpenseTableTextBlock" name="ScheduleOfOperatingLeaseExpenseTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
</xsd:schema>
