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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-11-20</periodOfReport>

    <issuer>
        <issuerCik>0002020354</issuerCik>
        <issuerName>West Bay BDC LLC</issuerName>
        <issuerTradingSymbol>NONE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001736027</rptOwnerCik>
            <rptOwnerName>GSAM Holdings LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 WEST STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10282</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOther>true</isOther>
            <otherText>See Remarks</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Units of limited liability company interests</value>
            </securityTitle>
            <transactionDate>
                <value>2024-11-20</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>0</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>27500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">GSAM Holdings LLC owns 27,500 common units of limited liability company interests (the &quot;Common Units&quot;) of West Bay BDC LLC (the &quot;Company&quot;). In addition, on November 20, 2024, the Company issued a capital call notice to its investors, pursuant to which GSAM Holdings LLC is obligated to make a capital contribution of approximately $1,350,000 on December 4, 2024 out of its $27,000,000 aggregate capital commitment to the Company; the Company is obligated to issue Common Units to GSAM Holdings LLC, provided such capital contribution is funded timely. The number of additional Common Units that will be issued to GSAM Holdings LLC in respect of its approximately $1,350,000 capital contribution will be determined by the then-applicable net asset value per unit, which has not yet been determined; GSAM Holdings LLC will amend this Form 4 once that determination has been made.</footnote>
    </footnotes>

    <remarks>GSAM Holdings LLC, a wholly owned subsidiary of The Goldman Sachs Group, Inc. and an affiliate of the issuer's adviser, does not concede that it is subject to Section 16 of the Securities Exchange Act of 1934, as amended, in respect of the issuer.</remarks>

    <ownerSignature>
        <signatureName>GSAM HOLDINGS LLC By: /s/ Alex Chi, authorized signatory</signatureName>
        <signatureDate>2024-11-22</signatureDate>
    </ownerSignature>
</ownershipDocument>
