<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-05-20</periodOfReport>

    <issuer>
        <issuerCik>0001758730</issuerCik>
        <issuerName>Tradeweb Markets Inc.</issuerName>
        <issuerTradingSymbol>TW</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001232995</rptOwnerCik>
            <rptOwnerName>BERNS STEVEN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>TRADEWEB MARKETS INC.</rptOwnerStreet1>
            <rptOwnerStreet2>1177 AVENUE OF THE AMERICAS</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10036</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>true</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A common stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-05-20</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>760</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>112.71</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3574</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">This transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 4, 2023.</footnote>
        <footnote id="F2">This amount includes 1,323 unvested RSUs in respect of the Class A Common Stock that are scheduled to vest on May 10, 2025, subject to the reporting person's continued service as a director through such vesting date or as may be pro-rated in accordance with the issuer's Non-Employee Director Compensation Policy, as disclosed in the issuer's Proxy Statement on DEF 14A filed with the SEC on March 28, 2024.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Douglas Friedman, Attorney-in-Fact for Steven Berns</signatureName>
        <signatureDate>2024-05-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
