X0306 4 2018-06-29 0 0001679268 MAMMOTH ENERGY SERVICES, INC. TUSK 0000874499 GULFPORT ENERGY CORP 3001 QUAIL SPRINGS PARKWAY OKLAHOMA CITY OK 73134 1 0 1 0 Common Stock 2018-06-29 4 S 0 1235600 38.01 D 9948522 D These shares of common stock, par value $0.01 per share ("Common Stock") of Mammoth Energy Services, Inc. (the "Issuer"), were sold by Gulfport Energy Corporation ("Gulfport") to the underwriters in a secondary public offering of Common Stock (the "Offering") at a price of $38.01 per share, which offering closed on June 29, 2018. Of these securities, 4,877 are unvested restricted stock units ("RSUs") that were granted under the Issuer's 2016 Equity Incentive Plan and were assigned to Gulfport by its director designee to the Issuer's board of directors under the terms of his employment with Gulfport. Such director designee previously reported the acquisition of the RSUs in his Form 4 filings and indicated that these were assigned to Gulfport. Of these 4,877 unvested RSUs, 2,222 will vest on October 19, 2018 and 2,655 will vest on the earlier of June 7, 2019 and the date of the Issuer's 2019 Annual Meeting of Stockholders. Each RSU represents a contingent right to receive one share of Common Stock of the Issuer. /s/ Keri Crowell, Chief Financial Officer 2018-07-03