UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): October 31, 2012

Marathon Petroleum Corporation

(Exact name of Registrant as specified in its charter)

539 South Main Street

Findlay, Ohio 45840

(Address of principal executive offices, including zip code)

(419) 422-2121

(Registrant’s telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

On October 31, 2012, MPLX LP (the “Partnership”), a subsidiary of Marathon Petroleum Corporation (“MPC”), completed its initial public offering (the “Offering”) of 19,895,000 common units representing limited partner interests in the Partnership (“Common Units”), which included 2,595,000 Common Units pursuant to the underwriters’ option to purchase additional Common Units, at $22.00 per Common Unit pursuant to a Registration Statement on Form S-1, as amended (File No. 333-182500), initially filed by the Partnership with the Securities and Exchange Commission (the “Commission”) pursuant to the Securities Act of 1933, as amended (the “Securities Act”), on July 2, 2012. The material provisions of the Offering are described in the prospectus, dated October 25, 2012, filed with the Commission on October 29, 2012, pursuant to Rule 424(b) under the Securities Act (the “Prospectus”).

Contribution, Conveyance and Assumption Agreement

The description of the Contribution Agreement (as defined below) provided below under Item 2.01 is incorporated in this Item 1.01 by reference. A copy of the Contribution Agreement is filed as Exhibit 10.1 to this Current Report on Form 8-K and incorporated herein by reference.

Omnibus Agreement

On October 31, 2012, in connection with the closing of the Offering, MPC entered into an Omnibus Agreement (the “Omnibus Agreement”) among the Partnership, MPLX GP LLC (the “General Partner”), Marathon Petroleum Company LP (“MPCLP”), MPL Investment LLC (“MPL Investment”), MPLX Operations LLC (the “Operating Company”), MPLX Terminal and Storage LLC (“MTS”), MPLX Pipe Line Holdings LP (“Pipe Line Holdings”), Marathon Pipe Line LLC (“MPL”) and Ohio River Pipe Line LLC (“ORPL”), that addresses the following matters:

So long as MPC controls the Partnership’s general partner, the Omnibus Agreement will remain in full force and effect. If MPC ceases to control the Partnership’s general partner, either party may terminate the Omnibus Agreement, provided that the indemnification obligations will remain in full force and effect in accordance with their terms.

The foregoing description is not complete and is qualified in its entirety by reference to the Omnibus Agreement, which is filed as Exhibit 10.2 to this Current Report on Form 8-K and incorporated herein by reference.

Relationships

Each of the Partnership, the General Partner, MPCLP, the Operating Company, MPC Investment LLC, MPLX Logistics Holdings LLC (“Logistics Holdings”), MPL, MPL Investment, MTS, Pipe Line Holdings and ORPL is a direct or indirect subsidiary of MPC. As a result, certain individuals, including officers and directors of MPC and the General Partner, serve as officers and/or directors of more than one of such other entities. As described in Item 2.01 below, the General Partner, as the general partner of the Partnership, holds 1,508,225 general partner units of the Partnership, which represents a 2% general partner interest in the Partnership and MPC, through Logistics Holdings, holds 17,056,515 Common Units and 36,951,515 subordinated units of the Partnership (“Subordinated Units”), which represent an approximate 71.6% limited partner interest in the Partnership.

Contribution, Conveyance and Assumption Agreement

On October 31, 2012, in connection with the closing of the Offering, the General Partner, the Operating Company, MPC Investment LLC, Logistics Holdings, MPL, MPL Investment, Pipe Line Holdings and ORPL entered into a Contribution, Conveyance and Assumption Agreement (the “Contribution Agreement”) with the Partnership. Immediately prior to the closing of the Offering, the following transactions, among others, occurred pursuant to the Contribution Agreement:

These transfers and distributions were made in a series of steps outlined in the Contribution Agreement. The foregoing description is not complete and is qualified in its entirety by reference to the full text of the Contribution Agreement, which is attached as Exhibit 10.1 to this Current Report on Form 8-K and incorporated herein by reference.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Date: November 6, 2012

Index to Exhibits