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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-04-30</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0001338613</issuerCik>
        <issuerName>Regency Energy Partners LP</issuerName>
        <issuerTradingSymbol>RGP</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001281086</rptOwnerCik>
            <rptOwnerName>MCREYNOLDS JOHN W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>3738 OAK LAWN AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75219</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <footnotes></footnotes>

    <remarks>In connection with the merger of a wholly owned subsidiary of Energy Transfer Partners, L.P. with and into Regency Energy Partners LP (&quot;RGP&quot;) effective on April 30, 2015, the reporting person resigned from the board of directors of Regency GP LLC, the general partner of Regency GP LP, the general partner of RGP. As a result, the reporting person is no longer subject to Section 16 in connection with his transactions in the equity securities of RGP and therefore will no longer report any such transactions on Form 4 or Form 5.</remarks>

    <ownerSignature>
        <signatureName>/s/ A. Troy Sturrock, as power of attorney</signatureName>
        <signatureDate>2015-05-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
