<SEC-DOCUMENT>0001209191-21-066339.txt : 20211123
<SEC-HEADER>0001209191-21-066339.hdr.sgml : 20211123
<ACCEPTANCE-DATETIME>20211123140501
ACCESSION NUMBER:		0001209191-21-066339
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20211119
FILED AS OF DATE:		20211123
DATE AS OF CHANGE:		20211123

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Beall Pamela K.M.
		CENTRAL INDEX KEY:			0001067429
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-35714
		FILM NUMBER:		211437184

	BUSINESS ADDRESS:	
		STREET 1:		C/O MARATHON PETROLEUM CORPORATION
		STREET 2:		539 S. MAIN STREET
		CITY:			FINDLAY
		STATE:			OH
		ZIP:			45840
		BUSINESS PHONE:		(419) 421-2159

	MAIL ADDRESS:	
		STREET 1:		C/O MARATHON PETROLEUM CORPORATION
		STREET 2:		539 S. MAIN STREET
		CITY:			FINDLAY
		STATE:			OH
		ZIP:			45840

	FORMER NAME:	
		FORMER CONFORMED NAME:	BEALL PAMELA KM
		DATE OF NAME CHANGE:	19980803

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MPLX LP
		CENTRAL INDEX KEY:			0001552000
		STANDARD INDUSTRIAL CLASSIFICATION:	PIPE LINES (NO NATURAL GAS) [4610]
		IRS NUMBER:				270005456
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		200 E. HARDIN STREET
		CITY:			FINDLAY
		STATE:			OH
		ZIP:			45840
		BUSINESS PHONE:		(419) 421-2159

	MAIL ADDRESS:	
		STREET 1:		200 E. HARDIN STREET
		CITY:			FINDLAY
		STATE:			OH
		ZIP:			45840
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc4.xml
<DESCRIPTION>FORM 4 SUBMISSION
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-11-19</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001552000</issuerCik>
        <issuerName>MPLX LP</issuerName>
        <issuerTradingSymbol>MPLX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001067429</rptOwnerCik>
            <rptOwnerName>Beall Pamela K.M.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MPLX LP</rptOwnerStreet1>
            <rptOwnerStreet2>200 E. HARDIN STREET</rptOwnerStreet2>
            <rptOwnerCity>FINDLAY</rptOwnerCity>
            <rptOwnerState>OH</rptOwnerState>
            <rptOwnerZipCode>45840</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Units (Limited Partner Interests)</value>
            </securityTitle>
            <transactionDate>
                <value>2021-11-19</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>134</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>29.68</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>43343</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Units (Limited Partner Interests)</value>
            </securityTitle>
            <transactionDate>
                <value>2021-11-19</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>416</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>29.68</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>42927</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Units (Limited Partner Interests)</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Revocable Trust</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">By Pamela K. M. Beall Trustee U.T.A. dated 12/26/16 f.b.o. Pamela K. M. Beall, et. al.</footnote>
    </footnotes>

    <remarks>The Reporting Person is a Director of MPLX GP LLC, the general partner of the Issuer.  The Issuer is managed by the directors and executive officers of MPLX GP LLC.</remarks>

    <ownerSignature>
        <signatureName>/s/ Molly R. Benson, Attorney-in-Fact for Pamela K.M. Beall</signatureName>
        <signatureDate>2021-11-23</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
