Exhibit 3.1

AMENDMENT NO. 7 TO

FIFTH AMENDED AND RESTATED AGREEMENT OF LIMITED

PARTNERSHIP OF

AMERICAN MIDSTREAM PARTNERS, LP

This Amendment No. 7 (this “ Amendment ”) to the Fifth Amended and Restated Agreement of Limited Partnership of American Midstream Partners, LP (the “ Partnership ”), dated as of October 26, 2017, as amended by Amendment No. 1 to the Fifth Amended and Restated Agreement of Limited Partnership of the Partnership, dated as of May 1, 2016, as amended by Amendment No. 2 to the Fifth Amended and Restated Agreement of Limited Partnership of the Partnership, dated as of October 31, 2016, as amended by Amendment No. 3 to the Fifth Amended and Restated Agreement of Limited Partnership of the Partnership, dated as of March 8, 2017, as amended by Amendment No. 4 to the Fifth Amended and Restated Agreement of Limited Partnership of the Partnership, dated as of May 25, 2017, as amended by Amendment No. 5 to the Fifth Amended and Restated Agreement of Limited Partnership of the Partnership, dated July 14, 2017, and as amended by Amendment No. 6 to the Fifth Amended and Restated Agreement of Limited Partnership of the Partnership, dated September 7, 2017 (as so amended, the “ Partnership Agreement ”), is hereby adopted effective as of September 30, 2017 by American Midstream GP, LLC, a Delaware limited liability company (the “ General Partner ”), as general partner of the Partnership, pursuant to the authority granted to it in  Section 13.1  of the Partnership Agreement. Capitalized terms used but not defined herein have the meaning given such terms in the Partnership Agreement.

WHEREAS ,  Section 13.1(g)  of the Partnership Agreement provides, in part, that the General Partner, without the approval of any Partner, may amend any provision of the Partnership Agreement in connection with the creation, authorization or issuance of any class or series of Partnership Interests and options, rights, warrants, appreciation rights, tracking and phantom interests or other economic interests in the Partnership relating to Partnership Interests;

WHEREAS , Section 13.3(c) of the Partnership Agreement provides that, if the General Partner determines an amendment adversely affects one or more classes of Partnership Interest, as compared to other classes of Partnership Interests, in any material respect, such amendment shall only be required to be approved by the adversely affected class or classes;

WHEREAS , the Board of Directors of the General Partner has determined that the standards specified in  Section 13.1(g) and Section 13.3(c)  are satisfied with respect to the amendments to the Partnership Agreement to be made by this Amendment upon approval of Record Holders of a majority of Outstanding Series C Units;

WHEREAS , Magnolia Infrastructure Holdings, LLC (“ MIH ”) is the sole record holder of the Outstanding Series C Units and has approved this Amendment; and

WHEREAS , the General Partner deems it in the best interests of the Partnership to effect this Amendment in order to amend the terms and provisions of the Series C Preferred Units as set forth herein.

NOW THEREFORE , the General Partner does hereby amend the Partnership Agreement as follows:

Commencing with the Quarter ending on June 30, 2016, the holders of the Series C Preferred Units Outstanding as of an applicable Record Date shall be entitled to receive cumulative distributions (each, a “ Series C Quarterly Distribution ”), prior to any other distributions made in respect of any Junior Interests pursuant to Section 6.4 or Section 6.5, in the amount set forth in this Section 5.14(b)(ii)(A) in respect of each Outstanding Series C Preferred Unit. All such distributions shall be paid Quarterly within forty-five (45) days after the end of each

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Quarter (each such payment date, a “ Series C Distribution Payment Date ”). For the Quarter ending June 30, 2016, and for each Quarter thereafter through and including the Quarter ending September 30, 2017, the Series C Quarterly Distribution on each Outstanding Series C Preferred Unit shall be paid a number of Series C PIK Preferred Units equal to the Series C PIK Payment Amount; provided that, in the discretion of the General Partner which determination shall be made prior to the Record Date for the relevant quarter, the Series C Quarterly Distribution may be paid in cash at the Series C Distribution Rate per Series C Preferred Unit (which, if paid in cash for the Quarter in which the Series C Issuance Date occurs, the amount payable shall be equal to the product of (I) the amount payable without regard to this parenthetical times (II) a fraction, of which the numerator is the number of days from and including the Series C Issuance Date to but excluding the date of such Quarter’s end, and the denominator is 91). With respect to the Quarter ending December 31, 2017 and all Quarters thereafter, the Series C Quarterly Distributions shall be paid entirely in cash at the Series C Distribution Rate per Series C Preferred Unit. If the Partnership establishes a Record Date for any distribution to be made by the Partnership on other Partnership Interests pursuant to Section 6.4 or Section 6.5, then the Record Date established pursuant to this Section 5.14(b)(ii)(A) for a Series C Quarterly Distribution in respect of any Quarter shall be the same Record Date established for any distribution to be made by the Partnership in respect of distributions on other Partnership Interests pursuant to Section 6.4 or Section 6.5 for such Quarter. Unless otherwise expressly provided, references in this Agreement to Series C Preferred Units shall include all Series C PIK Preferred Units Outstanding as of the date of such determination.

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IN WITNESS WHEREOF, the undersigned has executed this Amendment as of the date first written above and effective as of September 30, 2017.

[Signature Page to Amendment No. 7 to Limited Partnership Agreement.]