Document

October 10, 2017

VIA EDGAR

Securities and Exchange Commission

Division of Corporation Finance

100 F Street, NE

Washington, DC 20549

Re: MPLX LP
Registration Statement on Form S-3 (Registration No. 333-219795)

Ladies and Gentlemen:

On behalf of MPLX LP (the “Partnership”), the undersigned hereby requests, pursuant to Rule 461(a) promulgated under the Securities Act of 1933, that the Registration Statement on Form S-3 (File No. 333-219795) (the “Registration Statement”) of the Partnership be declared effective at 4:00 p.m. Eastern Time on Thursday, October 12, 2017, or as soon thereafter as practicable. The Partnership respectfully requests that you notify Kimberly J. Pustulka of Jones Day of such effectiveness by a telephone call to (216) 586-7002.

Please contact Kimberly J. Pustulka at (216) 586-7002 if you have any questions concerning this matter. Thank you for your continued attention to this matter.



	Very truly yours,
	MPLX LP

	By:	MPLX GP LLC, its General Partner

	By:	/s/ Molly R. Benson
	Name:	Molly R. Benson
	Title:	Vice President, Corporate Secretary and Chief Compliance Officer

cc: Kimberly J. Pustulka