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): February 14, 2019

ANTERO MIDSTREAM PARTNERS LP

(Exact name of registrant as specified in its charter)

Delaware |  | 001-36719 |  | 46-4109058
(State or Other Jurisdiction of Incorporation) |  | (Commission File Number) |  | (IRS Employer Identification Number)

1615 Wynkoop Street

Denver, Colorado 80202

(Address of Principal Executive Offices) (Zip Code)

Registrant’s Telephone Number, including area code: (303) 357-7310

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:

x Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company o

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. o

Item 7.01 Regulation FD Disclosure.

On February 14, 2019, Antero Midstream Partners LP (“Antero Midstream”) and Antero Midstream GP LP (“AMGP”) updated their monthly investor presentation. The updated investor presentation may be viewed on Antero Midstream’s website at www.anteromidstream.com, and a copy of the investor presentation is included as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated into this Item 7.01 by reference

Also on February 14, 2019, Antero Midstream held a conference call with analysts and investors to discuss fourth quarter and full year 2018 results. On the call, certain matters relating to the previously announced business combination transaction between Antero Midstream and AMGP were discussed. A transcript of the conference call is included as Exhibit 99.2 to this Current Report on Form 8-K, and the full text of such transcript is incorporated herein by reference. A copy of the presentation given during the conference call is included as Exhibit 99.3 to this Current Report on Form 8-K and is incorporated into this Item 7.01 by reference.

The information furnished in this Item 7.01 (including the exhibits) shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of that section, nor shall such information be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, regardless of any general incorporation language in such filing, except as shall be expressly set forth by specific reference in such filing.

Item 8.01 Other Events.

To the extent required by law, the information in Item 7.01 of this Form 8-K is incorporated into this Item 8.01.

NO OFFER OR SOLICITATION

The exhibits attached hereto include a discussion of the previously announced transaction between Antero Midstream and AMGP and certain of their affiliates (the “Transaction”). This communication is for informational purposes only and does not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval, in any jurisdiction, pursuant to the Transaction or otherwise, nor shall there be any sale, issuance, exchange or transfer of the securities referred to in this document in any jurisdiction in contravention of applicable law. No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of Securities Act of 1933, as amended.

ADDITIONAL INFORMATION AND WHERE TO FIND IT

In connection with the Transaction, AMGP has filed with the U.S. Securities and Exchange Commission (the “SEC”) a registration statement on Form S-4, that includes a joint proxy statement of Antero Midstream and AMGP and a prospectus of AMGP. The transaction will be submitted to Antero Midstream’s unitholders and AMGP’s shareholders for their consideration. Antero Midstream and AMGP may also file other documents with the SEC regarding the transaction. The registration statement on Form S-4 became effective on January 30, 2019, and the definitive joint proxy statement/prospectus is being delivered to Antero Midstream unitholders and AMGP shareholders of record as of January 11, 2019. This document is not a substitute for the registration statement and joint proxy statement/prospectus that has been filed with the SEC or any other documents that AMGP or Antero Midstream may file with the SEC or send to shareholders of AMGP or unitholders of Antero Midstream in connection with the transaction. INVESTORS AND SECURITY HOLDERS OF ANTERO MIDSTREAM AND AMGP ARE URGED TO READ THE REGISTRATION STATEMENT AND THE JOINT PROXY STATEMENT/PROSPECTUS REGARDING THE TRANSACTION AND ALL OTHER RELEVANT DOCUMENTS THAT ARE FILED OR WILL BE FILED WITH THE SEC, AS WELL AS ANY AMENDMENTS OR SUPPLEMENTS TO THESE DOCUMENTS, CAREFULLY AND IN THEIR ENTIRETY BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE TRANSACTION AND RELATED MATTERS.

Investors and security holders are able to obtain free copies of the registration statement and the joint proxy statement/prospectus and all other documents filed or that will be filed with the SEC by AMGP or Antero Midstream through the website maintained by the SEC at http://www.sec.gov. Copies of documents filed with the SEC by Antero Midstream will be made available free of charge on Antero Midstream’s website at http://investors.anteromidstream.com/investor-relations/AM, under the heading “SEC Filings,” or by directing a

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request to Investor Relations, Antero Midstream Partners LP, 1615 Wynkoop Street, Denver, Colorado 80202, Tel. No. (303) 357-7310. Copies of documents filed with the SEC by AMGP will be made available free of charge on AMGP’s website at http://investors.anteromidstreamgp.com/Investor-Relations/AMGP or by directing a request to Investor Relations, Antero Midstream GP LP, 1615 Wynkoop Street, Denver, Colorado 80202, Tel. No. (303) 357-7310.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

Exhibit No. |  | Description
99.1 |  | Antero Midstream Partners LP and Antero Midstream GP LP February 2019 Investor Presentation.
99.2 |  | Transcript of Antero Midstream Partners LP conference call held on February 14, 2019.
99.3 |  | Antero Midstream Partners LP and Antero Midstream GP LP Earnings Presentation dated February 14, 2018.

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SIGNATURES

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.

| ANTERO MIDSTREAM PARTNERS LP
| By: | Antero Midstream Partners GP LLC,
|  | its general partner
| By: | /s/ Glen C. Warren, Jr.
|  | Glen C. Warren, Jr.
|  | President and Secretary

Dated: February 14, 2019

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