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

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2007-04-17</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001376227</issuerCik>
        <issuerName>United States Natural Gas Fund, LP</issuerName>
        <issuerTradingSymbol>UNG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001359033</rptOwnerCik>
            <rptOwnerName>Nguyen Robert Long</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O VICTORIA BAY ASSET MANAGMENT, LLC</rptOwnerStreet1>
            <rptOwnerStreet2>1320 HARBOR BAY PARKWAY SUITE 145</rptOwnerStreet2>
            <rptOwnerCity>ALAMEDA</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94502</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <ownerSignature>
        <signatureName>/s/Suzan M. Barron, Attorney-in-fact</signatureName>
        <signatureDate>2007-04-24</signatureDate>
    </ownerSignature>
</ownershipDocument>
