FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * SEMPLE FRANK M   2. Issuer Name and Ticker or Trading Symbol MPLX LP [MPLX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) Vice Chairman (Last) (First) (Middle) C/O MPLX LP, 200 E. HARDIN STREET 3. Date of Earliest Transaction (Month/Day/Year) 12/04/2015 (Street) FINDLAY, OH 45840 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Units (Limited Partner Interests) 12/04/2015   A   284,565 (1) A (2) 284,565 D   Common Units (Limited Partner Interests) 12/04/2015   A   164,312 (3) A (2) 164,312 I Frank M Semple Revocable Trust Common Units (Limited Partner Interests) 12/04/2015   A   111,180 (4) A (2) 111,180 I Robin Y Semple 2012 Dynasty Trust Common Units (Limited Partner Interests) 12/04/2015   A   102,460 (5) A (2) 102,460 I Frank M Semple Dynasty Trust Common Units (Limited Partner Interests) 12/04/2015   A   48,777 (6) A (2) 48,777 I EK Holdings LLC

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
SEMPLE FRANK M C/O MPLX LP 200 E. HARDIN STREET FINDLAY, OH 45840	X		Vice Chairman

Signatures

/s/ Molly R. Benson, Attorney-in-Fact for Frank M. Semple		12/08/2015
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Received in exchange for 261,069 MarkWest Energy Partners, L.P. ("MarkWest") common units, including converted phantom units, in connection with the merger of Sapphire Holdco LLC, a wholly owned subsidiary of the Issuer, with and into MarkWest on December 4, 2015, with MarkWest as the surviving entity (the "Merger"). The Merger consideration for this transaction was 1.09 Issuer common units plus $6.20 in cash per MarkWest common unit or phantom unit converted in connection with the Merger, with cash paid in lieu of fractional units.
(2)	On the effective date of the Merger, the closing price of the Issuer's common units was $30.83 per unit.
(3)	Received in exchange for 150,745 MarkWest Energy Partners, L.P. ("MarkWest") common units in connection with the merger of Sapphire Holdco LLC, a wholly owned subsidiary of the Issuer, with and into MarkWest on December 4, 2015, with MarkWest as the surviving entity (the "Merger"). The Merger consideration for this transaction was 1.09 Issuer common units plus $6.20 in cash per MarkWest common unit or phantom unit converted in connection with the Merger, with cash paid in lieu of fractional units.
(4)	Received in exchange for 102,000 MarkWest Energy Partners, L.P. ("MarkWest") common units in connection with the merger of Sapphire Holdco LLC, a wholly owned subsidiary of the Issuer, with and into MarkWest on December 4, 2015, with MarkWest as the surviving entity (the "Merger"). The Merger consideration for this transaction was 1.09 Issuer common units plus $6.20 in cash per MarkWest common unit or phantom unit converted in connection with the Merger, with cash paid in lieu of fractional units.
(5)	Received in exchange for 94,000 MarkWest Energy Partners, L.P. ("MarkWest") common units in connection with the merger of Sapphire Holdco LLC, a wholly owned subsidiary of the Issuer, with and into MarkWest on December 4, 2015, with MarkWest as the surviving entity (the "Merger"). The Merger consideration for this transaction was 1.09 Issuer common units plus $6.20 in cash per MarkWest common unit or phantom unit converted in connection with the Merger, with cash paid in lieu of fractional units.
(6)	Received in exchange for 44,750 MarkWest Energy Partners, L.P. ("MarkWest") common units in connection with the merger of Sapphire Holdco LLC, a wholly owned subsidiary of the Issuer, with and into MarkWest on December 4, 2015, with MarkWest as the surviving entity (the "Merger"). The Merger consideration for this transaction was 1.09 Issuer common units plus $6.20 in cash per MarkWest common unit or phantom unit converted in connection with the Merger, with cash paid in lieu of fractional units.
Remarks: The Reporting Person is a Director and the Vice Chairman of MPLX GP LLC, the general partner of the Issuer. The Issuer is managed by the directors and executive officers of MPLX GP LLC.

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