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): July 17, 2015

Shell Midstream Partners, L.P.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (713) 241-6161

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 (see General Instruction A.2):

This Current Report on Form 8-K is being filed by Shell Midstream Partners, L.P. (the “Partnership”) to update the historical financial information of Mars Oil Pipeline Company, L.P. (“Mars”) and Bengal Pipeline Company LLC (“Bengal”), in which the Partnership owns equity interests, in accordance with Section 3-05 of Regulation S-X in connection with the filing of the Partnership’s registration statement on Form S-1 (No. 333-204906), originally filed with the Securities and Exchange Commission (the “SEC”) on June 12, 2015.

The audited historical financial statements of Mars, including the related notes thereto, as of December 31, 2013 and 2012, and for each of the years in the two-year period ended December 31, 2013 are provided in Exhibit 99.1 and incorporated herein by reference. The unaudited historical financial statements of Mars, including the related notes thereto, as of and for the nine months ended September 30, 2014 and 2013 are provided in Exhibit 99.2 and incorporated herein by reference.

The audited historical financial statements of Bengal, including the related notes thereto, as of December 31, 2013 and 2012, and for the years then ended, are provided in Exhibit 99.3 and incorporated herein by reference. The unaudited historical financial statements of Bengal, including the related notes thereto, as of and for the nine months ended September 30, 2014 and 2013 are provided in Exhibit 99.4 and incorporated herein by reference.

This Current Report on Form 8-K is also being filed to include the unaudited pro forma condensed consolidated financial statements of the Partnership as of and for the three months ended March 31, 2015 and for the year ended December 31, 2014 in accordance with Article 11 of Regulation S-X, which are provided in Exhibit 99.5 and incorporated herein by reference.

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SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: July 17, 2015

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INDEX TO EXHIBITS

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