UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 14A INFORMATION

PROXY STATEMENT PURSUANT TO SECTION 14(a)

OF THE SECURITIES EXCHANGE ACT OF 1934

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SemGroup Corporation

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SemGroup2017 Proxy Statement Notice of Annual Meeting of Stockholders to be held on May 17, 2017    

SEMGROUP CORPORATION

Two Warren Place

6120 S. Yale Avenue, Suite 1500

Tulsa, Oklahoma 74136-4231

April 13, 201712, 2019

LETTER FROM THE CHAIRMAN OF THE BOARD

TO OUR STOCKHOLDERS

On behalf of SemGroup’s Board of Directors, I am pleased to invite you to our Annual Meeting of Stockholders on May 17, 2017.15, 2019. The attached Proxy Statement contains important information about the business to be conducted at the Annual Meeting. Whether or not you plan to attend, we encourage you to vote your proxy as soon as possible so that your shares will be represented at the meeting.

This year we will vote on the election of seven directors and the ratification of Grant Thornton LLP’s selection as the company’s independent registered public accounting firm for 2017.2019. We will also conduct anon-binding advisory vote to approve the compensation of the company’s named executive officers a non-binding advisory vote regarding the frequency for which stockholders will have an advisory vote to approve the compensation paid to the company’s named executive officers, and a vote to approve an amendment to our Amended and Restated Certificaterestatement of Incorporation to authorize 4,000,000 shares of preferred stock.the Company’s equity incentive plan. In addition, leadership will provide a report on the company’s business and stockholders will have an opportunity to ask questions.

SemGroup’s Board of Directors is committed to strong corporate governance, stockholder transparency and consistent value creation for our investors. The Board and management team are comprised of individuals with decades of industry experience and diverse perspectives. As stewards of your investment in SemGroup, we are focused on achieving results for you.

Thank you for your continued support of SemGroup.

Thomas R. McDaniel

Chairman, Board of Directors

SEMGROUP CORPORATION

Two Warren Place

6120 S. Yale Avenue, Suite 1500

Tulsa, Oklahoma 74136-4231

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

OF SEMGROUP CORPORATION

AGENDA:

Record Date:You can vote if you were a stockholder of record on March 30, 2017.29, 2019.

Your vote is important regardless of the number of shares you own. Whether or not you expect to attend the meeting, we hope you will take the time to vote your shares. If you are a stockholder of record, you may vote over the Internet, by telephone or by completing and mailing the enclosed proxy card in the envelope provided. If your shares are held in “street name,” that is, held for your account by a broker or other nominee, you will receive instructions from the holder of record that you must follow for your shares to be voted.

By Order of the Board of Directors,

William H. Gault

Secretary

April 13, 201712, 2019

Important Notice Regarding the Availability of Proxy Materials for the 20172019 Annual Meeting of Stockholders to be Held on May 17, 2017:15, 2019: Stockholders may view the accompanying proxy statement, our form of proxy and our 20162018 Annual Report to Stockholders over the Internet by accessing our website athttp://www.semgroupcorp.com.www.semgroup.com.

SEMGROUP CORPORATION

Two Warren Place

6120 S. Yale Avenue, Suite 1500

Tulsa, Oklahoma 74136-4231

PROXY STATEMENT

FOR ANNUAL MEETING OF STOCKHOLDERS

To Be Held May 17, 201715, 2019

This proxy statement is furnished in connection with the solicitation by the Board of Directors of SemGroup Corporation, a Delaware corporation (the “Company,” “SemGroup,” “we,” “our” or “us”), of proxies to be voted at the Annual Meeting of Stockholders to be held on May 17, 2017,15, 2019, or at any adjournment thereof (the “Annual Meeting”), for the purposes set forth in the accompanying Notice of Annual Meeting. This proxy statement and accompanying proxy were first sent on or about April 13, 2017,12, 2019, to stockholders of record on March 30, 2017.29, 2019.

Holders of record of our Class A Common Stock (the “Class A Common Stock”) and Series A Cumulative Perpetual Convertible Preferred Stock (“Preferred Stock”) at the close of business on the record date, March 30, 2017,29, 2019, will be entitled to notice of, and to vote at, the Annual Meeting. As of March 30, 2017,29, 2019, there were 66,237,00679,531,367 shares of our Class A Common Stock outstanding and 350,000 shares of Preferred Stock outstanding. Each share of Class A Common Stock is entitled to one vote. Holders of shares of Preferred Stock are entitled to vote together with the holders of shares of Class A Common Stock as a single class. Each holder of shares of Preferred Stock is entitled to a number of votes equal to the number of votes such holder would have had if all shares of Preferred Stock held by such holder had been converted into shares of Class A Common Stock as of the record date. As of the record date, March 29, 2019, the outstanding shares of Preferred Stock were convertible into an aggregate of 11,518,608 shares of Class A Common Stock and such amount represents an equal number of votes that may be cast at the Annual Meeting in person or by proxy by holders of such stock. There are no other classes of common stock outstanding. Accordingly, the total number of shares entitled to vote at the Annual Meeting, giving effect to the Preferred Stock on anas-converted basis, is 91,049,975. There is no cumulative voting with respect to the election of directors.

For more information about this solicitation and voting, please see the Questions and Answers section below.

		other proposals.
Q:		How will my shares be voted if they are held in a broker’s name?
A:		If you hold your shares through an account with a bank or broker, the bank or broker may vote your shares on some matters even if you do not provide voting instructions. Brokerage firms have the authority under the New York Stock Exchange (“NYSE”) rules to vote shares on certain matters (such as the ratification of independent registered public accounting firm) when their customers do not provide voting instructions. However, on other “non-routine”“non-routine” matters, when the brokerage firm has not received voting instructions from its customers, the brokerage firm cannot vote the shares on that matter and a “brokernon-vote” occurs. The election of directors, the proposal seeking approval, on an advisory basis, of the compensation paid to our named executive officers, the advisory vote proposal regarding the frequency of an advisory vote on the compensation of our named executive officers, and the proposal to approve the amendment to ourSemGroup Corporation Equity Incentive Plan, as Amended and Restated, Certificate of Incorporation are considered “non-routine”“non-routine” matters. Accordingly, if you hold your shares through an account with a bank or broker, such organization may not vote your shares on these important proposals unless you have provided specific instructions as how to vote on these proposals. Please be sure to give specific voting instructions to your bank or broker so that your vote may be counted.

Our Amended and Restated Bylaws provide that our Board of Directors shall consist of not less than three nor more than eleven11 directors, as determined from time to time by resolution of the Board of Directors. The number of directors is currently fixed at seven. Directors are elected by the stockholders to serve for aone-year term expiring at the next annual meeting of stockholders and until their successors are duly elected and qualified, or until their earlier death, resignation or removal. The term of the current directors will expire at the Annual Meeting.

In accordance with the recommendation of the Nominating and Corporate Governance Committee, the Board of Directors has nominated Ronald A. Ballschmiede, Sarah M. Barpoulis, Carlin G. Conner, Karl F. Kurz, James H. Lytal, William J. McAdam and Thomas R. McDaniel to the Board of Directors. All of the nominees are presently directors of SemGroup. At the time of Mr. McAdam’s election to the Board of Directors in March 2017, he was recommended to the Nominating and Corporate Governance Committee by a third-party search firm.

The persons named as proxies in the accompanying proxy, who have been designated by the Board of Directors, intend to vote, unless otherwise instructed in such proxy, for the election of each of the nominees for director. Should any nominee named herein become unable for any reason to stand for election as a director, it is intended that the persons named in such proxy will vote for the election of such other person or persons as the Nominating and Corporate Governance Committee may recommend and the Board of Directors may propose to replace such nominee. We know of no reason why any of the nominees will be unavailable or unable to serve.

As noted earlier in the Questions and Answers section of this proxy statement, pursuant to our Corporate Governance Guidelines and Principles of the Board of Directors, as a requirement for nomination as a director, each nominee for director must tender his or her irrevocable resignation as a director conditioned upon (i) the director receiving more “withhold” votes than “for” votes (a “Majority Withhold Vote”) in an uncontested election and (ii) the Board accepting such resignation. In the event a nominee for director receives a Majority Withhold Vote in an uncontested election, the Nominating and Corporate Governance Committee of our Board of Directors shall promptly consider the tendered resignation and recommend to the Board the action to be taken with respect to such tendered resignation. The Nominating and Corporate Governance Committee is authorized to consider all factors it deems relevant to the best interests of the Company and its stockholders in reaching its recommendation. The Board will then act on such recommendation no later than 90 days following the certification of the election results. Following the Board’s decision, the Company will publicly disclose the Board’s decision and, if applicable, the reasons for rejecting the tendered resignation. Accordingly, the seven nominees with the largest number of “for” votes will be elected as directors, and in the event any nominee receives a Majority Withhold Vote, the resignation policy as summarized here will apply. The director resignation policy is set forth in our Corporate Governance Guidelines and Principles and is available on our website athttp://www.semgroupcorp.comwww.semgroup.com under the “Corporate Information—Governance—Governance Documents” caption on the “Investor Relations”“Investor” page.

Our Board of Directors recommends a vote“FOR” all nominees for directors.

Nominees for Directors

Set forth below is information with respect to each nominee for director, including information they have furnished as to his or her principal occupation or employment for the past five or more years and certain other directorships held. Each nominee’s information below also includes a summary of each individual’s experience, qualifications, attributes and skills that have led to the conclusion that each individual should serve as a director. In addition to the specific experiences, qualifications, attributes and/or skills set forth below, each nominee generally has demonstrated the highest professional and personal ethics,attained a broad rangeposition of experienceleadership in business, government and/or technology, the ability to provide insights and practical wisdom based on his or her field of endeavor; possesses corporate governance experience, business or financial expertise, integrity, objectivity and expertise,sound business judgment; has a commitment to enhancing stockholder value, compliance with legalserve the interests of all stockholders; and regulatory requirements andhas the ability to develop a good working relationship with other Board members and contribute to the Board’s working relationship with senior management of SemGroup. See “—Corporate Governance—Consideration of Director Nominees” below for additional information regarding director nominees and the nominating process.

Ronald A. Ballschmiede, age 61,63, has served as a director of SemGroup since 2009. He currently serves as Chairchair of the Nominating and Corporate Governance Committee of the Board of Directors and as a member of the Audit Committee of the Board of Directors.Board. Since November 2015, Mr. Ballschmiede has served as Executive Vice Presidentexecutive vice president and Chief Financial Officerchief financial officer of Sterling Construction Company, Inc. (“Sterling”), a leading heavy civil construction company that specializes in the building and reconstruction of transportation and water infrastructure projects. Mr. Ballschmiede served as a director of the general

partner of Rose Rock Midstream, L.P. (“Rose Rock” or “RRMS”), a publicly traded master limited partnership and subsidiary of SemGroup which owned and operated a diversified portfolio of midstream energy assets, from April 2016 to September 2016 when SemGroup acquired all of Rose Rock. From 2006 to 2015, Mr. Ballschmiede served as Executive Vice Presidentexecutive vice president and Chief Financial Officerchief financial officer of Chicago Bridge & Iron Co. N.V. (“CB&I”), a leading engineering, procurement and construction company that focuses on the energy and natural resource

industry. Prior to joining CB&I, he had a29-year career in public accounting, primarily focused on serving public companies in the manufacturing and construction industry. From 2002 to 2006, Mr. Ballschmiede served as a partner with Deloitte & Touche LLP. From 1977 to 2002, he was employed by Arthur Andersen, LLP, becoming a partner in its audit division in 1989. Mr. Ballschmiede graduated from Northern Illinois University with a Bachelor of Science degree in accounting and is a certified public accountant.

Mr. Ballschmiede provides the Board with extensive accounting and financial expertise gained from his service as Executive Vice Presidentexecutive vice president and Chief Financial Officerchief financial officer of Sterling and CB&I and his prior experience as a partner of Deloitte & Touche LLP and Arthur Andersen, LLP. His experience and knowledge make him a valuable contributor of financial, accounting and risk management expertise to the Board. Mr. Ballschmiede qualifies as an “audit committee financial expert” as defined by the U.S. Securities and Exchange Commission (“SEC”).

Sarah M. Barpoulis, age 52,54, has served as a director of SemGroup since 2009. She currently serves as Chairchair of the Audit Committee of the Board of Directors and as a member of the CompensationEnvironmental, Health, Safety and Social Responsibility Committee of the Board of Directors.Board. Since 2003, she has provided asset management and advisory services to the merchant energy sector through Interim Energy Solutions, LLC, a company she founded. From 1991 to February 2003, Ms. Barpoulis was employed with PG&E National Energy Group, Inc., now known as National Energy & Gas Transmission, Inc. (“National Energy”), a company that developed, built, owned and operated electric generating and natural gas pipeline facilities and provided energy trading, marketing and risk management services, last serving as Senior Vice President,senior vice president, commercial operations and trading. Ms. Barpoulis serves on the board of directors of South Jersey Industries, an energy services holding company with utility andnon-utility operations. She is also a director of South Jersey Energy Company and Educare, DC. She previously served as a director of Reliant Energy, Inc. from 2006 to 2008. Ms. Barpoulis has a master’s degree in business administration from the Tuck School of Business at Dartmouth College and a Bachelor of Science and engineering degree from Princeton University.

Ms. Barpoulis provides the Board with valuable executive-level leadership experience and risk management and business planning expertise obtained from her consulting services provided through Interim Energy Solutions, LLC and her varied roles of increasing responsibility with National Energy. She has receivedis a CertificateNational Association of Director Education fromCorporate Directors (NACD) Board Leadership Fellow, demonstrating her commitment to the NACDhighest standards of board leadership and also qualifies as an “audit committee financial expert” as defined by the SEC. Her risk management expertise, background and prior board and work experience allow her to be a valuable contributor to the Board.

Carlin G. Conner, age 49, has served as51, became president, chief executive officer, and a director and as President and Chief Executive Officer of SemGroup since 2014. Mr. Conner served as Chairman of the board of directors, Presidentin 2014 and Chief Executive Officer of the general partner of Rose Rock,began driving a publicly traded master limited partnershipstrategy toward focused growth and subsidiary of SemGroup which owned and operatedlong-term value creation. In 2000, he joined a diversified portfolio of midstream energy assets, from 2014 until September 2016 when SemGroup acquired all of Rose Rock. From 2012 until 2014, Mr. Conner served as managing directorsubsidiary of Oiltanking GmbH (“Oiltanking”), an independent worldwide storage provider of crude oil, refined petroleum products and liquid chemicalschemicals. During his nearly 14 years with Oiltanking and gases. Heits affiliates he focused on international business development while serving in various leadership roles. From 2012 to 2014, Mr. Conner served as a membermanaging director of Oiltanking and he served as chairman of the board of directors of the general partner of Oiltanking Partners, L.P., a publicly traded master limited partnership engaged in independent terminaling, storage and transportation of crude oil, refined petroleum products and liquefied petroleum gas, (“Oiltanking Partners”), from March 2011 until Marchto 2014.    From 2012 to 2014, and was elected Chairman in July 2011 in connection with the completion of Oiltanking Partners’ initial public offering. Mr. Conner also served as President and Chief Executive Officeran executive board member of Oiltanking Partner’s general partner from 2011 to 2012 and as President and Chief Executive OfficerMarquard & Bahls, AG, the parent company of Oiltanking, Holding Americas, Inc., a wholly owned subsidiary of Oiltanking GmbH from 2006 to 2012. Previously, from 2003 to 2006, he worked at Oiltanking GmbH’s corporate headquarters in Hamburg, Germany, where he was responsibleinstrumental in defining a new strategy for internationalthe energy supply, trading, and logistics business developmentacross Europe, the Americas, Asia, and sat on the boards of several Oiltanking GmbH ventures. He joined Oiltanking Houston, L.P. in 2000.Africa. He began his career at GATX Terminals Corporation and served in various roles, including operations and commercial management. From April 2014 to October 2014, Mr. Conner served on the Boardboard of Directorsdirectors of the general partner of NGL Energy Partners LP, a publicly traded master limited partnership. He also served as chairman of the board of directors, president and chief executive officer of the general partner of Rose Rock, a publicly traded master limited partnership engagedand subsidiary of the Company, which owned and operated a diversified portfolio of midstream energy assets, from 2014 until September 2016, when SemGroup acquired all of Rose Rock. Mr. Conner holds a bachelor’s degree in crude oil logistics, water solutions, liquids, retail propane, and refined products and renewables. He graduatedenvironmental science from McNeese State University, with a Bachelorwhere he was also named 2016 Distinguished Alumnus of Science degreethe Year. In addition, he completed INSEAD and MCE executive management training in environmental science.France and Belgium, respectively.

Mr. Conner provides the Board more than 2428 years of experience in the midstream industry and executive level experience gained through his services with Oiltanking GmbH and its affiliates as described above. He also has substantial board experience related to management and oversight of a midstream publicly traded master limited partnership. In addition, Mr. Conner serves as our Presidentpresident and Chief Executive Officerchief executive officer and is able to provide the Board valuable insight with respect to our management and operations. His industry knowledge, board experience and positions as Presidentpresident and Chief Executive Officerchief executive officer allow him to be a valuable contributor to the Board.

Karl F. Kurz, age 55,57, has served as a director of SemGroup since 2009. He currently serves on the Compensation Committee and on the Nominating and Corporate Governance Committee of the Board of Directors.Board. From 2009 through 2012, Mr. Kurz served as a

managing director of CCMP Capital Advisors, LLC, a global private equity firm. From 2000 to 2009, he was employed with Anadarko Petroleum Corporation, one of the largest independent oil and gas exploration and production companies in the world, last serving as Chief Operating Officerchief operating officer from December 2006. Prior to this position, he served Anadarko Petroleum Corporation in various

capacities, including as Senior Vice President,senior vice president, North America operations, midstream and marketing, General Manager,general manager, U.S. onshore, Senior Vice President,senior vice president, marketing, and Vice Presidentvice president marketing. Prior to joining Anadarko Petroleum Corporation, Mr. Kurz previously served as general manager of midstream and marketing for Vastar Resources, Inc. and, prior to that, as manager of crude oil marketing for ARCO Oil & Gas Company. He currently serves on the boards of American Water Works Company, Inc. (the largest and most geographically diverse publicly traded U.S. water and wastewater utility company), and WPX Energy, Inc. (anoil-focused energy company with operations in the U.S. Permian Williston and San Juan and one of the 20 largest U.S. producers based on total assets and market capitalization), Siluria Technologies (a developer of technologies for the commercial production of fuels and chemicals made from natural gas) and RTS Services (a real estate service company)Williston) and previously served on the boards of Siluria Technologies Inc., Western Gas Partners, Chaparral Energy, Inc. and, Global Geophysical Services, Inc., and RTS Services. Mr. Kurz graduated with a Bachelor of Science degree in petroleum engineering from Texas A&M University. He is also a graduate of Harvard University Business School’s advanced management program.

Mr. Kurz provides the Board extensive knowledge of the midstream energy services industry and executive-level leadership experience gained through his services provided to Anadarko Petroleum Corporation, Vastar Resources, Inc. and Arco Oil & Gas Company as described above. In addition, he brings public company board experience to our Board. His industry knowledge, executive-level leadership experience in relatively complex organizations and public company board experience allow Mr. Kurz to be a qualified and valuable contributor to the Board.

James H. Lytal, age 59,61, has served as a director of SemGroup since 2011. He currently serves as Chairchair of the Compensation Committee and as a member of the Audit Committee of the Board of Directors. Since 2009, Mr. Lytal has served as a senior advisor to Global Infrastructure Partners, a New York based partnership that invests in infrastructure assets globally. From 1994 to 2004, Mr. Lytal was Presidentpresident of Leviathan Gas Pipeline Partners, which later became El Paso Energy Partners, and then Gulfterra Energy Partners, where he served on the board of directors. In 2004, Gulfterra Energy Partners merged with Enterprise Products Partners, one of the largest publicly-traded energy partnerships in the United States,U.S., where Mr. Lytal served as Executive Vice Presidentexecutive vice president until 2009. From 1998 to 2008, he was directly involved in the development of over $3 billion in offshore platform and oil and gas pipeline projects. Having entered the energy industry in 1980, Mr. Lytal’s business experience includes midstream mergers, acquisitions and master limited partnership drop-downs, as well as onshore midstream and deepwater asset development and management. Mr. Lytal currently serves on the boardsboard of Archrock, Inc. (a U.S. natural gas contract compression services company). He previously served as a director of Azure Midstream Partner GP, LLC, the general partner of Azure Midstream Partners LP (afee-based, growth oriented limited partnership formed to develop, operate, and acquire midstream energy assets), until May 2017 and a director of Rice Midstream Management LLC, the general partner of Rice Midstream Partners LP (a fee-based, growth-oriented limited partnership formed by Rice Energy Inc. to own, operate, develop and acquire midstream assets in the Appalachian basin), and Archrock, Inc. (a U.S. natural gas contract compression services company). He until July 2018 when Rice Midstream Partners was acquired by EQT Midstream Partners, LP. Mr. Lytal graduated from the University of Texas at Austin with a Bachelor of Science degree in petroleum engineering.

Mr. Lytal has over 3538 years of experience in the midstream/MLP industry and provides the Board a broad range of knowledge and understanding in the management of midstream assets. His experience, executive leadership skills and familiarity with governance issues, particularly in the midstream sector, qualify him as a valuable and resourceful member of the Board.

William J. McAdam, age 65,67, has served as a director of SemGroup since March 2017. He currently serves onas the chairman of the Environmental, Health, Safety and Social Responsibility Committee and as a member of the Nominating and Corporate Governance Committee and Compensation Committee of the Board of Directors.Board. Mr. McAdam was Presidentpresident and Chief Executive Officerchief executive officer of Aux Sable Liquid Products Inc., Aux Sable Canada LP, and Aux Sable Midstream LLC (North American midstream energy companies) from 2000 to 2013. Prior to joining Aux Sable, he held progressively more senior positions with Imperial Oil and Exxon Chemical from 1974 to 1994 in the engineering, refining, fertilizer, petrochemicals, planning and natural gas liquids businesses in the United States and Canada. He began working with Aux Sable in 1995 during its development phase until 1998, and was President of Mapco Canada Energy Inc. from 1998 until 1999. Mr. McAdam joined Aux Sable in 1999 to lead thestart-up and development of the Aux Sable business in conjunction with the construction and commissioning of the Alliance Pipeline/Aux Sable rich gas system in 2000. He serves as a director of Seven Generations Energy Ltd., a Canadian exploration and production company and Tundra Energy Marketing Limited, a Canadian midstream service provider. Mr. McAdam previously served as a director of Canexus Corporation, a Canadian chemical manufacturing and handling company until it was acquired in March 2017 by ChemTrade Logistics Income Fund. Mr. McAdamHe earned a Bachelor of Science in Chemical Engineering from Queen’s University and a Master of Business Administration from McMaster University. HeMr. McAdam earned the ICD.D designation from the Institute of Corporate Directors in 2015.

Mr. McAdam has over 4244 years of experience in the energy industry and provides the Board a robust knowledge and understanding of the Canadian and U.S. energy sector. His executive leadership gained through his service to Aux Sable combined with his industry and public company board experience qualify him to make valuable contributions to the Board.

Thomas R. McDaniel, age 68,70, has served as a director of SemGroup since 2009 and as Chairmanchairman of the Board of Directors since January 1, 2017. Mr. McDaniel was Executive Vice President, Chief Financial Officerexecutive vice president, chief financial officer and Treasurertreasurer of Edison International, a

generator and distributor of electric power and investor in infrastructure and energy assets, before retiring in 2008 after 37 years of service. Prior to 2005, he was Chairman, Chief Executive Officerchairman, chief executive officer and Presidentpresident of Edison Mission Energy, Edison International’s power generation subsidiary specializing in the development, acquisition, construction, management and operation of power production

facilities. Prior to that, Mr. McDaniel served as Presidentpresident and Chief Executive Officerchief executive officer of Edison Capital, a capital and financial services business subsidiary which invests worldwide in energy and infrastructure projects. Mr. McDaniel serves on the board of directors of SunPower Corporation, a manufacturer of high-performance solar electric systems worldwide for residential, commercial and utility-scale power plant customers, and of Tendril, Inc., a provider of energy services management solutions.customers. He has previously served on the board of directors of Cypress Envirosystems, a subsidiary of Cypress Semiconductor Corp., and of Aquion Energy, Inc., a manufacturer of proprietary Aqueous Hybrid Ion (AHI™) batteries and battery systems for long-duration, stationary energy storage applications.applications, and Tendril, Inc., a provider of energy services management solutions. Mr. McDaniel graduated from the University of California at Los Angeles with a Bachelor of Science degree.

Mr. McDaniel has extensive operational and financial management experience gained from his roles of increasing responsibility with Edison International. In addition, he provides the Board with his experience as a director and audit committee member of a public company. Mr. McDaniel’s operational and financial management experience and his understanding of the role of board of directors allow him to be a valued contributor to the Board and as Chairman.chairman.

Our Board of Directors is committed to sound and effective governance practices. Our Board of Directors has adopted corporate governance guidelines titled “Corporate Governance Guidelines and Principles of the Board of Directors” which provide a framework of governance principles and procedures to assist in the operation of the Board of Directors.Board. The guidelines address, among other things, director qualifications, director independence, composition of the Board, director responsibilities, Board committees, Board self-evaluation and management review and succession. The Nominating and Corporate Governance Committee reviews the guidelines periodically, and the guidelines may be amended at any time upon recommendation by Nominating and Corporate Governance Committee and approval of the Board of Directors.Board.

SemGroup has a Code of Business Conduct and Ethics for directors, officers (including the chief executive officer, principal financial officer and principal accounting officer) and employees. SemGroup also has a separate Code of Ethics for the Chief Executive Officerchief executive officer and Senior Financial Officers,senior financial officers, which contain provisions specifically applicable to our chief executive officer and senior financial officers, including our chief financial officer and chief accounting officer.

The Corporate Governance Guidelines and Principles, the Code of Business Conduct and Ethics and the Code of Ethics for the Chief Executive Officerchief executive officer and Senior Financial Officerssenior financial officers are available on our website athttp://www.semgroupcorp.comwww.semgroup.com under the “Corporate Governance—Governance Documents” caption on the “Investor Relations”“Investor” page and copies of these documents may also be obtained in print by any stockholder who requests them from our corporate secretary. If we amend the Code of Business Conduct and Ethics or Code of Ethics for the Chief Executive Officerchief executive officer and Senior Financial Officerssenior financial officers or waive the Code of Business Conduct and Ethics or Code of Ethics for the Chief Executive Officerchief executive officer and Senior Financial Officerssenior financial officers with respect to the chief executive officer, principal financial officer or principal accounting officer, we will post the amendment or waiver, as the case may be, at the same location on our website.

Director Independence. Our Board of Directors has adopted a formal set of categorical independence standards with respect to the determination of director independence based on the NYSE listing standards. These standards are set forth in our Director Nomination Policy which is available on our website athttp://www.semgroupcorp.comwww.semgroup.com under the “Corporate Governance—Governance Documents” caption on the “Investor Relations”“Investor” page. The provisions of the Director Nomination Policy regarding director independence meet and in some areas exceed the listing standards of the NYSE. In order to be considered independent, a director must be determined to have no material relationship with the Company other than as a director.

Under the Director Nomination Policy, an “independent director” is one who:

For purposes of determining a “material relationship,” the following standards are utilized:

For purposes of these independence standards, (i) immediate family members of a director include the director’s spouse, parents, stepparents, children, stepchildren, siblings, mother- andfather-in-law, sons- anddaughters-in-law, and brothers- andsisters-in-law and anyone (other than domestic employees) who shares the director’s home and (ii) the term “primary business affiliation” means an entity of which the director is a principal/executive officer or in which the director holds at least a 5% equity interest.

In accordance with the Director Nomination Policy and the current director independence standards of the NYSE, the Board undertook its annual review of director and director nominee independence. During this review, the Board considered transactions and relationships between each director and director nominee or any member of his or her immediate family and the Company and its subsidiaries and affiliates. The Board also considered whether there were any transactions or relationships between directors, nominees or any member of their immediate family (or any entity of which a director, director nominee or an immediate family member is an executive officer, general partner or significant equity holder). As provided in the Director Nomination Policy and the NYSE independence standards, the purpose of this review was to determine whether any such relationships or transactions existed that were inconsistent with a determination that the director or nominee is independent.

The Board of Directors has affirmatively determined that each of Mr. Ballschmiede, Ms. Barpoulis, Mr. Kurz, Mr. Lytal, Mr. McAdam and Mr. McDaniel, current directors of the Company, are independent under the standards set forth in the Director Nomination Policy and the current director independence standards of the NYSE. Mr. Conner is not considered to be independent because of his current employment as our Presidentpresident and Chief Executive Officer.chief executive officer.

Board Meetings and Attendance. The Board held 2213 meetings during the year ended December 31, 2016.2018. During that year, each of our directors attended at least 75 percent of the aggregate number of Board meetings and meetings held by all committees on which he or she then served. In addition, the Board of Directors took action four timesone time during 20162018 by unanimous written consent.

Director Attendance at Annual Meeting of Stockholders. Each director is encouraged to participate in our annual meetings of stockholders. Each of our directors then serving attended our 20162018 annual meeting of stockholders.

Board Leadership Structure and Role in Risk Oversight. While we currently separate the offices of Chairmanchairman of the Board and Chief Executive Officer,chief executive officer, our Corporate Governance Guidelines and Principles specify that the Board of Directors has no policy mandating the separation of the offices of Chairmanchairman of the Board and Chief Executive Officer,chief executive officer, as our Board believes it is in our best interest to have flexibility in selecting our Chairmanchairman and board leadership structure as future circumstances may warrant. Our Board’s oversight of risk management (discussed below) has had no effect on our leadership structure.

Our Board of Directors has six independent members and only onenon-independent member. A number of our independent board members are currently serving or have served as members of senior management or as directors of other public companies. Our Audit, Compensation, and Nominating and Corporate Governance and Environmental, Health, Safety and Social Responsibility Committees are comprised solely of independent directors, each with a different independent director serving as chair of the committee. We believe that the number of independent, experienced directors that make up our Board of Directors, along with the independent oversight of the Board by thenon-executive Chairman, chairman, benefits our Company and our stockholders.

Our Board of Directors is responsible for oversight of our enterprise-wide risk and has approved our Comprehensive Risk Management Policy that reflects an enterprise-wide approach to risk management and considers both financial andnon-financial risks. Our Comprehensive Risk Management Policy and its associated framework is designed to ensure we:

The Audit Committee of our Board of Directors has oversight responsibilities for the implementation of, and compliance with, our Comprehensive Risk Management Policy on behalf of the Board of Directors.Board.

While the Board of Directors oversees our risk management, our management is responsible forday-to-day risk management processes. We have established an executive management committee, comprised of corporate officers, which oversees the financial andnon-financial risks associated with all activities governed by our Comprehensive Risk Management Policy and its associated framework, including: asset operations; marketing; investments, divestitures, and other capital expenditures and dispositions; credit risk management; and other strategic activities. We also have a separate risk management group that is assigned responsibility for independently monitoring compliance with, reporting on, and enforcing the provisions of our Comprehensive Risk Management Policy.

Board Committees. The Board of Directors has a standing Audit Committee, Compensation Committee, and Nominating and Corporate Governance Committee.Committee, and Environmental, Health, Safety and Social Responsibility Committee (“EHS Committee”). Each of the current members of each of the committees qualifies as an “independent” director under the current listing standards of the NYSE.

The table shows the current membership of the Committees and identifies our independent directors:

Name

Ronald A. Ballschmiede

Sarah M. Barpoulis

Carlin G. Conner

Karl F. Kurz

James H. Lytal

William J. McAdam

Thomas R. McDaniel

Audit

X

X*

X

Compensation

X

X

X*

Nominating and Corporate Governance

X*

X

X*

X

Nominating and Corporate Governance

X*

X

Independent Directors

X

X

X

X

EHS

X

X

X*

Independent Directors

X

X

X

X

X

X

* Denotes Committee Chairman.

Audit Committee. The Board of Directors has determined that Ronald A. Ballschmiede and Sarah M. Barpoulis qualify as “audit committee financial experts” within the meaning of the regulations of the SEC. The Audit Committee has a written charter, which is available on our website athttp://www.semgroupcorp.com.www.semgroup.com. We have in place and circulated a “whistleblower policy” entitled “Audit Committee Accounting and Ethics Concern Resolution Policy.” The Audit Committee assists the Board of Directors in fulfilling its responsibilities by providing oversight relating to:

A more detailed description of the Audit Committee’s responsibilities can be found in its charter.

The Audit Committee held eightsix meetings during 2016.2018.

Compensation Committee. The Compensation Committee has a written charter, which is available on our website athttp://www.semgroupcorp.com.www.semgroup.com. The Compensation Committee reviews and takes action for and on behalf of the Board of Directors with respect to management compensation policies and practices, including (i) including:

In addition, the Compensation Committee recommends the form and amount ofnon-employee director compensation to the Board of Directors, and the Board of Directors makes the final determination. The Compensation Committee has authority under its charter to obtain advice and seek assistance from compensation consultants and from internal and outside legal, accounting and other advisors.

In considering and recommending the compensation ofnon-employee directors, the Compensation Committee may consider such factors as it deems appropriate, including historical compensation, level of compensation necessary to attract and retainnon-employee directors meeting our desired qualifications and market data. In connection with the review of ournon-employee director compensation by the Compensation Committee in 2016,2018, the Compensation Committee retained Pearl Meyer & Partners (“Pearl Meyer”) to provide market information onnon-employee director compensation, including annual board and committee retainers, board and committee meeting fees, committee chairperson fees and stock-based compensation. The Compensation Committee has discretion under its charter to form and delegate some or all of its authority to subcommittees composed entirely of independent directors. During 2016,2018, the Compensation Committee did not form or utilize a subcommittee. More information describing the Compensation Committee’s processes and procedures for considering and determining executive compensation, including the role of our Chief Executive Officerchief executive officer and consultants in determining or recommending the amount or form of executive compensation, is included in the Compensation Discussion and Analysis under “Executive Compensation” below.

The Compensation Committee held eightseven meetings during 2016. In addition, the Compensation Committee took action three times during 2016 by unanimous written consent.2018.

Nominating and Corporate Governance Committee. The Nominating and Corporate Governance Committee has a written charter, which is available on our website athttp://www.semgroupcorp.com.www.semgroup.com. The Nominating and Corporate Governance Committee is responsible for identifying and recommending nominees for election orre-election as directors by stockholders at each annual meeting of stockholders, as well as candidates to fill vacancies on the Board of Directors should vacancies occur. The Nominating and Corporate Governance Committee has the authority under its charter to retain a professional search firm to identify candidates. The Nominating and Corporate Governance Committee is also responsible for developing and recommending to the Board of Directors our Corporate Governance Guidelines and Principles.

The Nominating and Corporate Governance Committee held threefive meetings during 2016.2018.

Environmental, Health, Safety, and Social Responsibility Committee. The EHS Committee has a written charter, which is available on our website at http://www.semgroup.com. The EHS Committee assists the Board in overseeing the Company’s health, safety, and environmental policies, programs, performance, and initiatives and reviews the Company’s social responsibility practices.

The EHS Committee was formed in September 2018 and held two meetings during 2018.

Consideration of Director Nominees. The Nominating and Corporate Governance Committee has adopted a Director Nomination Policy, which is available on our website athttp://www.semgroupcorp.com.www.semgroup.com. The Committee will consider director candidates submitted to it by other directors, employees and stockholders. The Committee may engage professional search firms to assist it in identifying and evaluating potential candidates. Any stockholder recommendations of candidates proposed for consideration by the Nominating and Corporate Governance Committee should include the candidate’s name and qualifications for director and should be addressed to: Secretary, Two Warren Place, 6120 S. Yale Avenue, Suite 1500, Tulsa, Oklahoma 74136. In addition, as described below, our Amended and Restated Bylaws permit stockholders to nominate directors for consideration at a meeting of stockholders.

In considering prospective nominees for the Board, the Nominating and Corporate Governance Committee will endeavor to find individuals of high integrity who have a solid record of accomplishment in their chosen fields and who possess the qualifications, qualities and skills to effectively represent the best interests of all stockholders. Candidates are selected for their ability to exercise good judgment and provide practical insights and diverse perspectives. The Nominating and Corporate Governance Committee considers the following qualifications at a minimum to be required in recommending to the Board potential new Board members or the continued service of existing members:

Other than the foregoing, there are no stated minimum criteria for director nominees, although the Nominating and Corporate Governance Committee may also consider such other factors as it may deem are in the best interests of the Company and its

stockholders. The Nominating and Corporate Governance Committee does, however, believe it appropriate for at least one member of the Board to meet the criteria for an “audit committee financial expert” as defined by the rules of the SEC. When considering potential nominees for the Board, the Committee will consider the criteria above and each potential nominee’s individual skills and qualifications in context of the current composition of the Board and needs of the Board at such time. In connection therewith, the Committee will consider diversity in professional background, experience, expertise, perspective, age, gender and ethnicity with respect to Board composition as a whole, although the Committee does not have a specific diversity policy. With respect to diversity, in accordance with our Corporate Governance Guidelines and Principles, particular emphasis is placed on identifying candidates whose experiences, qualitiesskills and skillscharacteristics complement and augment thosethe make-up of other Board members with respect to the Board of Directors as a group.whole and the needs of the Board given the circumstances of the Company.

The Company’s Corporate Governance Guidelines and Principles provide that a director who changes substantially the principal occupation, position or responsibility he or she had when elected to the Board should volunteer to resign from the Board. The Nominating and Corporate Governance Committee will have the opportunity to evaluate the continued appropriateness of Board membership under the facts and circumstances and make a recommendation to the Board whether to accept the resignation or request the director to continue to serve on the Board.

Our Amended and Restated Bylaws permit stockholders to nominate directors for consideration at an annual meeting of stockholders. To nominate a director, stockholders must follow the procedures specified in our Amended and Restated Bylaws that require advance notice and certain other information.information and requirements. Stockholders must submit the candidate’s name and qualifications in writing to our Secretary at the following address: Secretary, SemGroup Corporation, Two Warren Place, 6120 S. Yale Avenue, Suite 1500, Tulsa, Oklahoma 74136. The written notice must be received by our Secretary not later than the close of business on the 90th day nor earlier than the close of business on the 120th day prior to the first anniversary of the preceding year’s annual meeting. The notice must contain certain information required under our Amended and Restated Bylaws, including, among other things, (i) the nominee’s name, age, business and residential addresses, written consent to being named in the proxy statement and to serving as director if elected, relationships between the nominee and the stockholder submitting the nomination, a completed and signed questionnaire, representation and agreement as required by our Amended and Restated Bylaws, and any other information relating to such person as would be required to be disclosed in solicitations of proxies for election of directors pursuant to Section 14(a) under the Securities Exchange Act of 1934 and (ii) with respect to the stockholder submitting the nomination and anyone acting in concert with that stockholder, the name and business addresses of the stockholder and the person acting in concert with the stockholder, a representation that the stockholder is a record holder of Class A Common Stockstock entitled to vote at such meeting (and will continue to be through the date of the meeting) and intends to appear in person or by proxy at the meeting to nominate the person or persons specified in the notice, a description of all agreements, arrangements or understandings between or among the stockholder and any other person or persons with respect to the nomination and the class and number of shares of Class A Common Stockstock beneficially owned by the stockholder and any person acting in concert with that stockholder.stockholder, a description of any voting arrangements with respect to securities of the Company, a description of any dividend rights separate from the underlying shares of the Company, a description of any performance-based fees the person is entitled to based on any increase or decrease in the value of shares of the Company, and a summary of any material discussion regarding the nomination between the stockholder submitting the nomination and other holders of our stock. For further information, stockholders may contact our Secretary at our principal executive offices for a copy of the relevant provisions of our Amended and Restated Bylaws.

Any single stockholder, or group of stockholders, that has beneficially owned more than 5% of our outstanding common stock for at least one year as of the date of recommendation may recommend nominees for director to the Nominating and Governance Committee by delivering a written notice to our Secretary that satisfies the notice, information, and consent requirements of the Director Nomination Policy. The Committee will evaluate such recommended nominees against the same criteria that it uses to evaluate other nominees. The notice must be received by the Nominating and Governance Committee no later than the date that is 120 calendar days prior to the anniversary of the date that our proxy statement was released to stockholders in connection with the previous year’s annual meeting. The notice must include, among other things, proof of the required stock ownership, proof of identification of the stockholder(s) submitting the proposal, information regarding the proposed candidate to the Board of Directors and a signed statement by the candidate with respect to certain matters. The notice should be addressed to: Secretary, Two Warren Place, 6120 S. Yale Avenue, Suite 1500, Tulsa, Oklahoma 74136.

Executive Sessions. Each regularly scheduled meeting of the Board of Directors includes an executive session of thenon-management directors. These sessions are chaired by the independent,non-executive Chairman chairman of the Board. If ournon-management directors include any directors who have been determined not to be independent by the Board, the Board will schedule an executive session of just the independent directors at least once each year.

Communications with the Board of Directors. Stockholders who wish to communicate with our Board of Directors or any of its committees may send written communications to: Board of Directors, SemGroup Corporation, Two Warren Place, 6120 S. Yale Avenue, Suite 1500, Tulsa, Oklahoma 74136. In addition, stockholders and other interested parties may communicate with the Chairmanchairman of the Board or with thenon-management directors as a group by writing to: Chairman of the Board, Two Warren Place, 6120 S. Yale Avenue, Suite 1500, Tulsa, Oklahoma 74136.

In accordance with Section 14A of the Securities Exchange Act of 1934, we are providing our stockholders the opportunity to approve, on an advisory andnon-binding basis, the compensation of our named executive officers as disclosed in this proxy statement.

This proposal, commonly known as a “say-on-pay”“say-on-pay” proposal, gives our stockholders the opportunity to express their views on our named executive officers’ compensation. This vote is not intended to address any specific item of compensation, but rather the overall compensation of our named executive officers and our compensation objectives, philosophy and practices described in this proxy statement. As discussed in greater detail in the “Compensation Discussion and Analysis” in this proxy statement, our compensation program is designed to, among other things:

We believe that our compensation program, with its balance of base salary, short-term and long-term incentives and benefits, fairly accomplishes our objectives. We believe our executive compensation program has allowed us to attract and build a leadership team which is focused on our business objectives and helped us achieve many of our 20162018 objectives as noted in “2016“2018 Business Highlights” under “Executive Compensation—Compensation Discussion and Analysis—Executive Summary” in this proxy statement.

Accordingly, our Board of Directors recommends our stockholders vote in favor of thesay-on-pay proposal as set forth in the following resolution:

“RESOLVED, that the compensation of the Company’s named executive officers as disclosed in its Proxy Statement for the 20172019 Annual Meeting of Stockholders pursuant to the compensation disclosure rules of the Securities and Exchange Commission, including the Compensation Discussion and Analysis, the executive compensation tables and the corresponding narrative discussion, is approved.”

This vote is advisory, and therefore nonbinding. Stockholders are strongly encouraged to read the Compensation Discussion and Analysis, the accompanying compensation tables, and the related narrative disclosure. The Board of Directors and the Compensation Committee expect to take into account the outcome of the vote in connection with their evaluation of our compensation program to the extent they can determine the stockholders’ concerns associated with any significant negative voting results. At our 20162018 annual meeting, the compensation of our named executive officers as disclosed in last year’s proxy statement was approved by over 98.58%97.4% (more than 98.59%97.7% if abstentions are excluded from the calculation) of the votes cast on the proposal, which demonstrated strong stockholder support for our executive compensation approach.

As determined by the Board of Directors, weWe have provided our stockholders with the opportunity to vote on the compensation to our named executive officers at every annual meeting of stockholders since 2011. An

As determined by the Board of Directors, we will continue to provide our stockholders with the opportunity to vote on the compensation to our named executive officers at every annual meeting of stockholders until the next required advisory vote at the 2023 annual meeting of stockholders on the frequency of stockholder advisory votes on the compensation of our named executive officers is being conducted again in connection with the Annual Meeting as set forth in Proposal 3.officers.

Our Board of Directors recommends that you vote “FOR”“FOR” the approval, on an advisory basis, of the compensation of our named executive officers.

In accordance with Section 14A of the Securities Exchange Act of 1934, we are also including in this proxy statement a separate resolution to enable our stockholders to vote, on an advisory and non-binding basis, for their preference as to how frequently we should seek future say-on-pay advisory votes on the compensation of our named executive officers. Stockholders may indicate whether future advisory votes on executive compensation should occur every one, two or three years. Stockholders also may, if they wish, abstain from casting a vote on this proposal.

This advisory vote on the frequency of future say-on-pay votes must be provided to stockholders at least once every six years. At the May 2011 annual meeting of our stockholders, our Board of Directors recommended, and the stockholders voted on an advisory basis in favor of, holding the say-on-pay vote every year. The Board accepted our stockholders’ recommendation, and stockholders have been provided with the opportunity to vote to approve, on an advisory and non-binding basis, the compensation of our named executive officers every year.

Our Board of Directors continues to believe that a frequency of “every year” for the advisory vote on executive compensation is the most optimal interval for conducting and responding to a say-on-pay vote. The Board believes that an annual advisory vote on executive compensation will allow our stockholders to provide direct input on the philosophy, policies and practices of our executive compensation program as disclosed in the proxy statement every year. An annual advisory vote on our executive compensation will provide a better opportunity for stockholders to constructively communicate with us regarding their views on our executive compensation program on a timely basis.

The proxy card and the Internet and the telephone proxy submission procedures each will provide stockholders with the opportunity to choose among four options: holding the vote every one, two or three years, or abstaining. Stockholders will not be voting to approve or disapprove our Board of Directors’ recommendation.

Although this advisory vote on the frequency of the say-on-pay vote is nonbinding, our Board of Directors will take into account the outcome of the vote when considering the frequency of future advisory votes on executive compensation. The Board may decide that it is in the best interests of our stockholders and us to hold an advisory vote on executive compensation more or less frequently than the frequency receiving the most votes cast by our stockholders.

You may cast your vote on your preferred voting frequency by choosing the option of one year, two years or three years or abstain from voting when you vote in response to the resolution set forth below.

“RESOLVED, that the option of every one year, two years or three years that receives the highest number of votes cast for this resolution will be determined to be the preferred frequency with which the Company is to hold a stockholder vote to approve, on an advisory basis, the compensation of the named executive officers.”

Our Board of Directors recommends that you vote “FOR” the option of every one year as the preferred frequency for the holding of future advisory votes on compensation of our named executive officers.

PROPOSAL 43 RATIFICATION OF APPOINTMENT OF INDEPENDENT    REGISTERED PUBLIC ACCOUNTING FIRM

On February 26, 2017, theThe Audit Committee has appointed Grant Thornton LLP as our independent registered public accounting firm (“independent auditor”) for the fiscal year ending December 31, 2017.2019. A proposal will be presented at the Annual Meeting asking the stockholders to ratify the appointment of Grant Thornton LLP as our independent auditor for 2017.2019. If the stockholders do not ratify the appointment of Grant Thornton LLP, the Audit Committee will reconsider the appointment. Even if the appointment is ratified, the Audit Committee, in its sole discretion, may change the appointment at any time during the year if the Audit Committee determines that a change is in the best interests of SemGroup.

A representative of Grant Thornton LLP will be present at the Annual Meeting and will have the opportunity to make a statement, if he or she desires to do so, and respond to appropriate questions.

Our Board of Directors recommends a vote“FORFOR”” the ratification of Grant Thornton LLP as our independent auditor for the fiscal year ending December 31, 2017.2019.

Change in Independent Registered Public Accounting Firm

SemGroup recently solicited bids for audit services for 2017 from several independent auditors, including BDO USA, LLP (“BDO USA”), which had been our independent auditor since 2008. As a result of this process and following careful consideration and deliberation, on February 26, 2017, the Audit Committee approved the engagement of Grant Thornton LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2017 and to perform interim review procedures related to the financial statements included in our quarterly reports on Form10-Q, beginning with the quarter endingended March 31, 2017. Also on February 26, 2017, the Audit Committee dismissed BDO USA as the Company’s independent registered public accounting firm. BDO USA was notified of the Committee’s decision on February 27, 2017.

BDO USA’s audit reports on the Company’s consolidated financial statements for the two most recent fiscal years ended December 31, 2016 and 2015, did not contain an adverse opinion or disclaimer of opinion, nor were they qualified or modified as to uncertainty, audit scope or accounting principles generally accepted in the United States (“US GAAP”).

During the Company’s two most recent fiscal years ended December 31, 2016 and 2015 and through the subsequent interim period through February 26, 2017, (i) there were no disagreements between the Company and BDO USA on any matters of US GAAP or practices, financial statement disclosure or auditing scope or procedure, which disagreements, if not resolved to the satisfaction of BDO USA, would have caused BDO USA to make reference to the subject matter of the disagreement in its reports on the Company’s consolidated financial statements for such years, and (ii) there were no “reportable events” as defined in Item 304(a)(1)(v) of RegulationS-K.

During the Company’s two most recent fiscal years ended December 31, 2016 and 2015, and during the subsequent interim period through February 26, 2017, we did not consult with Grant Thornton LLP with respect to (i) the application of accounting principles to a specified transaction, either completed or proposed, or the type of audit opinion that might be rendered on the Company’s consolidated financial statements, and neither a written report was provided to the Company nor oral advice was provided to the Company that Grant Thornton LLP concluded was an important factor considered by the Company in reaching a decision as to the accounting, auditing or financial reporting issue; or (ii) any matter that was either the subject of a disagreement as defined in Item 304(a)(1)(iv) of RegulationS-K and the related instructions or a “reportable event” as described in Item 304(a)(1)(v) of RegulationS-K.

Fees of Independent Registered Public Accounting Firm

The following table sets forth the fees for professional services provided to us by BDO USA,Grant Thornton LLP for fiscal 20162018 and 2015:2017:

Audit fees include those related to the audit of our consolidated financial statements, reviews of our quarterly financial statements, audits of the financial statements of our subsidiaries (as required by statute, by our credit agreements, by partnership agreements and by regulations of the SEC), and the audit of internal control over financial reporting as required by Section 404 of

the Sarbanes-Oxley Act of 2002. Audit fees also include services performed in connection with other filings with the SEC. Audit-related fees are related to the audits of benefit plans. Tax fees are related to certain international tax consultation services.

Audit CommitteePre-Approval Policies and Procedures

The Audit Committeepre-approves all audit and permissiblenon-audit services by its independent registered public accountant prior to the receipt of such services. All services for the fiscal years ended December 31, 20162018 and 20152017 set forth in the table above werepre-approved by the Audit Committee.

Introduction

At the Annual Meeting our stockholders will be asked to approve the SemGroup Corporation Equity Incentive Plan, as amended and restated (which is referred to in this proposal as the “Restated Equity Incentive Plan”), including an amendment to increase the total number of shares of Class A Common Stock available for issuance under the current plan from 3,581,635 shares to 7,181,635 shares, an increase of 3,600,000 shares. The SemGroup Corporation Equity Incentive Plan (which is referred to in this proposal as the “Current Equity Incentive Plan”) was originally adopted in connection with our reorganization in November 2009 and previously amended and restated effective as of May 17, 2016. The Restated Equity Incentive Plan was recommended by the Compensation Committee of the Board of Directors and adopted by the Board of Directors on April 2, 2019, subject to stockholder approval at the Annual Meeting. If such approval is not received, the Restated Equity Incentive Plan will not take effect and the Current Equity Incentive Plan will continue as currently in effect.

While the primary purpose of amending the plan is to permit an increase in the shares available for awards under the plan, we are also proposing to amend the plan to:

Why Submit the Restated Equity Incentive Plan to a Vote of Our Stockholders?

We are submitting the Restated Equity Incentive Plan to a vote of the stockholders to comply with NYSE rules. Stockholder approval will also allow us to grant incentive stock options within the meaning of Section 422 of the Internal Revenue Code of 1986, as amended (the “Code”), under the Restated Equity Incentive Plan.

Current Awards Outstanding

Set forth below is information regarding the estimated shares outstanding under the Current Equity Incentive Plan as of March 22, 2019.

Rationale for the Request for Additional Shares

The Restated Equity Incentive Plan will be our only plan for providing equity compensation awards for shares of SemGroup to our employees. The Board of Directors believes that the Restated Equity Incentive Plan is in the best interests of our stockholders and SemGroup, as equity awards granted under this plan provide a key compensation component to our officers and key employees and help to attract, retain and motivate key personnel, align employee and stockholder interests and link employee compensation to company performance. Based on the number of shares available for future awards, we may have an insufficient number of shares for our 2020 long-term incentive awards. We typically grant long-term incentive awards in the first quarter of each year. In order to give us the flexibility to continue to provide long-term incentive awards as a key component of our overall compensation program, the Compensation Committee has recommended to the Board that we request our stockholders approve an additional 3,600,000 shares for issuance under the Restated Equity Incentive Plan.

As part of the Compensation Committee’s recommendation to the Board to approve the request for an increase in the total number of shares that will be available for issuance under the Restated Equity Incentive Plan, the Compensation Committee solicited advice from Pearl Meyer, its independent compensation consultant, to provide an analysis of the potential total dilution impact and expected plan life of the Restated Equity Incentive Plan under our historical compensation program. Specifically, the Compensation Committee considered the following:

Historical Burn Rate.We are committed to managing the use of our equity incentives prudently to balance the benefits equity compensation brings to our compensation programs with the dilution it causes our stockholders. As part of its analysis when considering the proposed share increase, the Compensation Committee considered our “burn rate,” or the number of shares subject to equity awards granted in each of the past three years, divided by the weighted average basic number of shares

outstanding for each of those years. Over the past three fiscal years, our burn rate has averaged approximately 1.29 percent, which is well below industry burn rate benchmarks published by leading proxy advisory firms.

Overhang.As a way of measuring the cumulative impact of our equity plan on our stockholders, the Compensation Committee also considered our level of overhang, consisting of the number of shares subject to equity awards outstanding under the Current Equity Incentive Plan plus the number of shares currently available to be granted under the plan. The Compensation Committee then considered the potential overhang resulting from the request for additional shares and determined that the addition of 3,600,000 shares to the plan share reserve was reasonable. Following plan approval, our total overhang will be approximately 7.0 percent of the total outstanding shares of our Class A Common Stock.

Expected Duration. If the Restated Equity Incentive Plan is approved by our stockholders, the estimated total number of shares of our Class A Common Stock reserved for future grants of awards under the Restated Equity Incentive Plan would be approximately 3,617,692 and represent approximately 4.6 percent of our total outstanding shares of Class A Common Stock as of March 22, 2019. If the Restated Equity Incentive Plan is approved by our stockholders, based on historical usage, we estimate that the shares available for issuance under the Restated Equity Incentive Plan would be sufficient for approximately three to five years. Expectations regarding future share usage could be affected by a number of factors such as hiring; the rate at which shares are returned to the plan share reserve as a result of the expiration, forfeiture or cash settlement of awards; the consequences of acquiring other companies; and other factors. It is our current practice to grant stock-based compensation awards to key employees on an annual basis during the first quarter of each fiscal year and tonon-employee directors in the second quarter of each fiscal year, in each case based on targeted dollar values that are generally competitive with industry peers. Fluctuations in our stock price may result in stock-based awards for a given year requiring a larger or smaller number of shares in order to capture the same grant date fair value as a prior year’s award, which impacts that rate at which we utilize shares for compensation purposes. While the Compensation Committee believes that the assumptions it used are reasonable, future share usage may differ from current expectations.

Our Plan Terms are Aligned with Stockholder Interests

The following features of the Restated Equity Incentive Plan protect the interests of our stockholders:

Summary of the Restated Equity Incentive Plan

The following is a summary of the material features of the Restated Equity Incentive Plan. This summary is qualified in its entirety by the full text of the Restated Equity Incentive Plan, a copy of which is included asAnnex A to this proxy statement.

Purpose. The purpose of the Restated Equity Incentive Plan is to attract, retain and motivate our officers, employees andnon-employee directors providing services to our Company, its subsidiaries and affiliates, and to promote our business by providing participants with appropriate incentives in our long-term success.

Types of Awards. The Restated Equity Incentive Plan authorizes the grant of the following types of awards: nonqualified stock options, incentive stock options, stock appreciation rights, restricted stock, other stock-based awards, including restricted stock units, performance-based compensation awards and cash awards.

Shares Available; Certain Limitations. A total of 7,181,635 shares of our Class A Common Stock are authorized for issuance pursuant to all awards granted under the Restated Equity Incentive Plan. The number of shares available for granting incentive stock options under the Restated Equity Incentive Plan may not exceed 4,308,981 shares. The number of shares that may be issued under the Restated Equity Incentive Plan or under outstanding awards is adjusted in the event of certain corporate events or transactions as discussed below under “Adjustment of Awards.” The shares available for issuance under the Restated Equity Incentive Plan may consist, in whole or in part, of authorized and unissued shares or shares held in treasury.

Shares subject to awards that expire or are forfeited, cancelled, terminated or settled in cash do not count as shares issued under the Restated Equity Incentive Plan and are again available for awards under the Restated Equity Incentive Plan. However, shares exchanged or withheld as payment in connection with any option or stock appreciation right or exchanged by a participant or withheld to satisfy tax withholding obligations related to any award are not available for subsequent awards under the Restated Equity Incentive Plan. In addition, notwithstanding that a stock appreciation right is settled by delivery of a net number of shares, the full number of shares underlying such stock appreciation right shall not be available for subsequent awards under the Restated Equity Incentive Plan.

The number of shares with respect to awards denominated in shares that may be granted to any participant in any calendar year under the Restated Equity Incentive Plan may not exceed 500,000 shares. Additionally, (i) the grant date fair value of awards granted to anon-employee director may not exceed $500,000 in the aggregate during any calendar year and (ii) no participant will be granted cash awards payable in the aggregate in excess of $5,000,000 during any calendar year.

Eligible Participants. Awards may be granted tonon-employee directors, officers and employees of our Company and officers and employees of our subsidiaries and affiliates. However, incentive stock options may be granted only to employees. As of December 31, 2018, we had 871 employees, including 257 employees in Canada, and sixnon-employee directors.

Administration. The Restated Equity Incentive Plan is administered by the Compensation Committee of our Board of Directors or any committee subsequently designated by our Board of Directors to administer the Restated Equity Incentive Plan. The Compensation Committee has the discretion to determine the individuals to whom awards may be granted under the Restated Equity Incentive Plan, the number of shares of our Class A Common Stock subject to each award, the type of award, the manner in which such awards will vest and the other conditions applicable to awards. The Compensation Committee is empowered to clarify, construe or resolve any ambiguity in any provision of the Restated Equity Incentive Plan or any award agreement and adopt such rules, forms, instruments and guidelines for administering the Restated Equity Incentive Plan as it deems necessary or proper. Awards may, in the discretion of the Compensation Committee, be made in assumption of, or in substitution for, outstanding awards previously granted by the Company or any of its subsidiaries or affiliates or a company acquired by the Company or with which the Company combines. All actions, interpretations and determinations by the Compensation Committee or by our Board of Directors are final and binding.

Award Agreements. Awards granted under the Restated Equity Incentive Plan will be evidenced by award agreements that provide additional terms and conditions associated with such awards, as determined by the Compensation Committee in its discretion. In the event of any conflict between the provisions of the Restated Equity Incentive Plan and any such award agreement, the provisions of the Restated Equity Incentive Plan will control.

Stock Options. The Compensation Committee will determine the exercise price and other terms for each stock option granted under the Restated Equity Incentive Plan and whether the options are nonqualified stock options or incentive stock options, but the exercise price of any option will not be less than 100% of the fair market value of a share of our Class A Common Stock on the date of grant, as determined by the Compensation Committee. Incentive stock options may be granted only to employees and are subject to certain other restrictions. A participant may exercise an option by written notice and payment of the exercise price in cash, shares or a combination of cash and shares, as determined by the Compensation Committee, or, if there is a public market for the shares, through the delivery of irrevocable instructions to a broker to sell shares obtained upon the exercise of the option and promptly deliver payment to us out of the proceeds of the exercise price for the shares purchased. The maximum term of any option granted under the Restated Equity Incentive Plan is ten years from the date of grant.

Stock Appreciation Rights. The Compensation Committee may grant stock appreciation rights, or SARs, independent of, or in tandem with, a stock option. The exercise price per share of a SAR will be determined by the Compensation Committee, but will not be less than 100% of the fair market value of a share of our Class A Common Stock on the date of grant, as determined by the Compensation Committee. The Compensation Committee will determine the other terms applicable to SARs. The maximum term of any SAR granted under the Restated Equity Incentive Plan is ten years from the date of grant. Generally, each SAR will entitle a participant, upon exercise, to receive an amount equal to:

Payment may be made in shares of our Class A Common Stock, cash, other property or any combination thereof, all as determined by the Compensation Committee.

Restricted Stock. The Compensation Committee may grant an award of restricted stock under the Restated Equity Incentive Plan. Restricted stock awards are a grant of a specified number of shares of our Class A Common Stock, which are subject to forfeiture upon the occurrence of specified events. Each award agreement evidencing a restricted stock grant will specify the period(s) of restriction, the conditions under which the restricted stock may be forfeited to us and such other provisions as the Compensation Committee may determine, subject to the terms of the Restated Equity Incentive Plan. The Compensation Committee will determine and set forth in the award agreement whether a recipient of restricted stock shall have the right to exercise voting rights with respect to the restricted stock during the restricted period and/or have the right to receive dividends on the restricted stock during the restricted period.

Other Stock-Based Awards; Restricted Stock Units. The Compensation Committee may award other types of stock-based awards under the Restated Equity Incentive Plan that are valued, in whole or in part, by reference to, or based on the fair market value of our Class A Common Stock, including restricted stock units. Restricted stock units may entitle the holder to receive a specified number of shares of our Class A Common Stock, cash, or a combination of shares and cash, upon the completion of a specified period of service, the occurrence of an event and/or the attainment of specified performance objectives. Subject to the provisions of the Restated Equity Incentive Plan, the Compensation Committee will determine whether such other stock-based awards will be settled in cash, shares of our Class A Common Stock or a combination of cash and such shares, and all other terms and conditions of such awards.

Cash Awards. Awards that are payable solely in cash may be granted under the Restated Equity Incentive Plan, and such cash awards may be granted with value and payment contingent upon the achievement ofpre-established performance measures or other performance goals.

Performance-Based Compensation Awards. The Compensation Committee may design any award that is intended to be performance-based compensation. The grant, vesting, crediting and/or payment of performance-based compensation will be based on the achievement of objective performance goals established in writing by the Compensation Committee. Performance goals may be based on one or more of the following measures: (i) consolidated earnings before or after taxes (including earnings before interest, taxes, depreciation and amortization); (ii) net income; (iii) operating income; (iv) earnings per share; (v) book value per share; (vi) return on stockholders’ equity; (vii) expense management; (viii) return on investment; (ix) improvements in capital structure; (x) profitability of an identifiable business unit or product; (xi) maintenance or improvement of profit margins; (xii) stock price; (xiii) market; (xiv) revenue or sales; (xv) costs; (xvi) cash flows; (xvii) working capital; (xviii) return on assets; (xix) growth, maintenance or refurbishment projects; (xx) staff training; (xxi) dividends; (xxii) subsidiary distributions; (xxiii) safety; (xxiv) corporate social responsibility policy implementation; (xxv) corporate strategic initiatives; and (xxvi) such other measures selected or defined by the Compensation Committee at the time such performance goals are established.

Transferability of Awards; Conditions and Restrictions on Shares. Unless otherwise determined by the Compensation Committee, awards granted under the Restated Equity Incentive Plan are not transferable other than by will or the laws of descent and distribution. The Compensation Committee may impose such transfer restrictions on any shares received in connection with an award as it may deem advisable or desirable. These restrictions may include, but shall not be limited to, a requirement that the participant hold the shares received for a specified period of time or a requirement that a participant represent and warrant in writing that the participant is acquiring the shares for investment and without any present intention to sell or distribute such shares.

Stockholder Rights. Except as otherwise provided in the applicable award agreement, a participant has no rights as a stockholder with respect to shares of our Class A Common Stock covered by any award until the participant becomes the record holder of such shares.

Adjustment of Awards. In the event of a corporate event or transaction such as a merger, consolidation, reorganization, recapitalization, separation, stock dividend, stock split, reverse stock split, split up,spin-off, combination or similar event or transaction, in order to prevent dilution or enlargement of participants’ rights under the Restated Equity Incentive Plan, the Compensation Committee will make certain adjustments to awards, including, in its sole discretion, substitution or adjustment of the number and kind of shares or cash or other property that may be issued under the Restated Equity Incentive Plan or under particular awards, the grant price or purchase price applicable to outstanding awards, and other value determinations applicable to the Restated Equity Incentive Plan or outstanding awards.

Change of Control; Qualifying Termination. In the event we experience a change of control (as defined below), the Compensation Committee may, but is not obligated to, make adjustments to the terms and conditions of outstanding awards, including, without limitation:

Unless otherwise determined by the Compensation Committee and evidenced in an award agreement, and subject to the ability of the Compensation Committee to accelerate the vesting and/or lapse of restrictions on awards upon a change of control, in the event that (i) a change of control occurs, and (ii) a participant’s employment or service is terminated by the Company or its affiliate without “cause” or by the participant for “good reason” (as those terms are defined in the Restated Equity Incentive Plan) within 24 months following the change of control, then:

For purposes of the Restated Equity Incentive Plan, a “change of control” will, unless otherwise specified in an applicable award agreement, mean the occurrence of any of the following events:

Payment of Withholding Taxes. We may withhold from any payments or stock issuances under the Restated Equity Incentive Plan, or collect as a condition of payment, any taxes required by law to be withheld. Subject to the Compensation Committee’s right to approve, any award recipient may, but is not required to, satisfy his or her withholding tax obligation by electing to have us withhold, from the shares the participant would otherwise receive, shares of our Class A Common Stock having a value equal to the minimum amount required to be withheld or such other amount that will not cause adverse accounting consequences for the Company and is permitted under applicable withholding rules promulgated by the Internal Revenue Service or other applicable governmental entity.

Amendment and Termination. The Compensation Committee may amend or terminate the Restated Equity Incentive Plan or any award agreement at any time; provided that stockholder approval will be needed for an amendment if:

No amendment or termination is permitted without the consent of the participants, if such amendment or termination would materially diminish the participants’ rights under the Restated Equity Incentive Plan or any award.

No awards will be granted after May 15, 2029.

Compliance with Code Section 409A. To the extent that the Restated Equity Incentive Plan or awards are subject to Section 409A of the Code, the Compensation Committee may, in its sole discretion and without a participant’s prior consent, amend the Restated Equity Incentive Plan or awards, adopt policies and procedures, or take any other actions as are necessary or appropriate to either exempt the Restated Equity Incentive Plan or any award from the application of Section 409A of the Code, preserve the intended tax treatment of any such award or comply with the requirements of Section 409A of the Code.

U.S. Federal Income Tax Consequences

The Company believes that under present U.S. federal income tax laws the following are the U.S. federal income tax consequences generally arising with respect to awards under the Restated Equity Incentive Plan. The following summary does not purport to be a complete description of all applicable rules, and these rules (including those summarized below) are subject to change. The summary does not address the effects of any state or local ornon-U.S. tax laws that may be applicable.

Nonqualified Stock Options. In general, no taxable income is realized by a participant upon the grant of a nonqualified stock option. Rather, at the time of exercise of the nonqualified stock option, the participant will be treated as receiving compensation (taxable as ordinary income and subject to withholding and employment taxes) in an amount equal to the fair market value of a share of our Class A Common Stock at such time, less the exercise price paid. The participant’s basis in the Class A Common Stock for purposes of determining gain or loss on a subsequent sale or disposition of such shares generally will be the fair market value of our Class A Common Stock on the date the participant exercises such option. Any subsequent gain or loss generally will be taxable as a capital gain or loss. We generally should be entitled to a federal income tax deduction at the time and for the same amount as the participant recognizes ordinary income.

Incentive Stock Options. In general, no taxable income is realized by a participant upon the grant of an incentive stock option. Additionally, if the applicable employment-related requirements are met, the participant will not recognize taxable income at the time of exercise. However, the excess of the fair market value of our Class A Common Stock received over the option purchase price is an item of tax preference income potentially subject to the alternative minimum tax. If any of the requirements for incentive stock options under the Code are not met, the incentive stock option will be treated as a nonqualified stock option and the tax consequences described above for nonqualified stock options will apply. Once an incentive stock option has been exercised by a participant, if the stock acquired upon exercise is held for a minimum of two years from the date of grant and one year from the date of exercise, the gain or loss (in an amount equal to the difference between the fair market value on the date of sale and the exercise price) upon disposition of the stock will be treated as a long-term capital gain or loss, and we will not be entitled to any deduction. If the holding period requirements are not met, the excess of the fair market value of the stock on the date of exercise over the exercise price (less any diminution in value of the stock after exercise) will be treated as compensation (taxed as ordinary income and subject to withholding and employment taxes) and we will be entitled to a deduction to the extent

of the amount so included in the income of the holder. Appreciation in the stock subsequent to the exercise date will be taxed as long-term or short-term capital gain, depending on whether the stock was held for more than one year after the exercise date.

Restricted Stock.A participant generally will not be taxed upon the grant of restricted stock, but rather will recognize ordinary income in an amount equal to the fair market value of the shares at the time the shares are no longer subject to a “substantial risk of forfeiture” (within the meaning of the Code). We generally will be entitled to a deduction at the time when, and in the amount that, the participant recognizes ordinary income on account of the lapse of the restrictions. A participant’s tax basis in the shares will equal their fair market value at the time the restrictions lapse, and the participant’s holding period for capital gains purposes will begin at that time. Any cash dividends paid on the restricted stock before the restrictions lapse will be taxable to the participant as additional compensation (and not as dividend income). Under Section 83(b) of the Code, a participant may elect to recognize ordinary income at the time the restricted stock is awarded in an amount equal to the fair market value at that time, notwithstanding the fact that such restricted stock is subject to restrictions and a substantial risk of forfeiture. If such an election is made, no additional taxable income will be recognized by such participant at the time the restrictions lapse, the participant will have a tax basis in the shares equal to their fair market value on the date of their award, and the participant’s holding period for capital gains purposes will begin at that time. We generally will be entitled to a tax deduction at the time when, and to the extent that, ordinary income is recognized by such participant. A participant who makes an election under Section 83(b) and then forfeits the stock is not entitled to deduct any amount as a result of the forfeiture notwithstanding that the participant included the fair market value of the stock in income at the time of the election.

Restricted Stock Units. In general, the grant of restricted stock units will not result in income for the participant or in a tax deduction for us. Upon the settlement of such an award in cash or shares, the participant will recognize ordinary income equal to the aggregate value of the payment received, and we generally will be entitled to a tax deduction at the same time and in the same amount.

Stock Appreciation Rights.A participant who is granted a SAR generally will not recognize ordinary income upon receipt of the SAR. Rather, at the time of exercise of such SAR, the participant will recognize ordinary income for income tax purposes in an amount equal to the value of any cash received and the fair market value on the date of exercise of any shares received. We generally will be entitled to a tax deduction at such time and in the same amount, if any, that the participant recognizes as ordinary income. The participant’s tax basis in any common shares received upon exercise of a SAR will be the fair market value of the common shares on the date of exercise, and if the shares are later sold or exchanged, then the difference between the amount received upon such sale or exchange and the fair market value of such shares on the date of exercise will generally be taxable as long-term or short-term capital gain or loss (if the shares are a capital asset of the participant) depending upon the length of time such shares were held by the participant.

Other Awards. With respect to other awards granted under the Plan, including share bonuses, other share-based awards and cash awards, generally when the participant receives payment with respect to an award, the amount of cash and/or the fair market value of any common shares or other property received will be ordinary income to the participant, and we generally will be entitled to a tax deduction at the same time and in the same amount.

If, on a change of control of our Company, the exercisability or vesting of an award is accelerated, any excess on the date of the change of control of the fair market value of the shares or cash issued under accelerated awards over the purchase price of such shares, if any, may be characterized as “parachute payments” (within the meaning of Section 280G of the Code) if the sum of such amounts and any other such contingent payments received by the employee equals or exceeds an amount equal to three times the “base amount” for such employee. The base amount generally is the average of the annual compensation of such employee for the five years ending before the year in which such change in ownership or control occurs. An “excess parachute payment,” with respect to any employee, is the excess of the parachute payments to such person, in the aggregate, over and above such person’s base amount. If the amounts received by an employee upon achange-in-control are characterized as parachute payments, such employee will be subject to a 20 percent excise tax on the excess parachute payment and we will be denied any deduction with respect to such excess parachute payment.

New Plan Benefits

The types and amounts of benefits that will be awarded under the Restated Equity Incentive Plan are not currently determinable. Awards granted under the Restated Equity Incentive Plan are within the discretion of the Compensation Committee, and the Compensation Committee has not determined future awards or who might receive them. Information on equity-based awards recently granted under the Current Equity Incentive Plan to each of our named executive officers is provided below under the headings “Summary Compensation Table” and “Grants of Plan-Based Awards During 2018.” The closing price for the Class A Common Stock on the NYSE on March 29, 2019, was $14.74.

Our Board of Directors recommends a vote“FOR” the approval of the SemGroup Equity Incentive Plan, as Amended and Restated, to increase the number of shares authorized thereunder by 3,600,000 shares and make other changes to the terms of the plan.

Introduction

Our Board of Directors has approved an amendment to our Amended and Restated Certificate of Incorporation, which we refer to as the “Preferred Stock Amendment,” to provide authority to issue up to 4,000,000 shares of preferred stock, par value $0.01 per share, and has directed that the Preferred Stock Amendment be submitted to our stockholders for approval at the Annual Meeting. The proposed Preferred Stock Amendment is set forth in Annex A attached to this proxy statement, which amendment has been marked to indicate additions to our Amended and Restated Certificate of Incorporation as underlined text and deletions to our Amended and Restated Certificate of Incorporation as strike-outs.

Authorization of Preferred Stock

We are not currently authorized under our Amended and Restated Certificate of Incorporation to issue any shares of preferred stock. The Preferred Stock Amendment authorizes our Board of Directors to issue, from time to time, up to 4,000,000 shares of preferred stock in one or more series with such designations, powers, preferences and rights as may be determined by our Board of Directors. The specific terms of a particular series of preferred stock would be described in a certificate of designation relating to that series. Our Amended and Restated Certificate of Incorporation currently authorizes (i) 90,000,000 shares of Class A Common Stock, par value $0.01 per share, and (ii) 10,000,000 shares of Class B Common Stock, par value $0.01 per share. As of the record date, March 30, 2017, there were 66,237,006 shares of Class A Common Stock outstanding and no shares of Class B Common Stock outstanding.

If the Preferred Stock Amendment is approved, no further stockholder approval would be required prior to the issuance of the authorized shares of preferred stock, except as may be required by applicable law or NYSE rules. The authorization of the preferred stock will not have any immediate effect on the rights of our existing stockholders. However, in connection with the issuance of preferred stock, our Board of Directors would have the authority to designate and issue series of our preferred stock with dividend, liquidation, conversion, voting or other rights that may be superior to those of our common stock. The effects of the issuance of preferred stock upon holders of our common stock may include, among other things: (i) a preference in the payment of dividends to holders of preferred stock, which may restrict our ability to declare dividends on our common stock; (ii) dilution of voting power if holders of preferred stock are given voting rights; (iii) dilution of equity interests and voting power if the preferred stock is convertible, and converted into, common stock; or (iv) a preference in payments upon liquidation to holders of preferred stock, which may limit liquidation payments on our common stock.

Reasons for the Preferred Stock Amendment

Our Board of Directors has determined that the authorization of preferred stock is advisable and in the best interests of SemGroup and its stockholders because it will provide SemGroup with the flexibility to consider and respond to future business needs and opportunities as they arise from time to time, including in connection with capital raising, financing and acquisition needs or opportunities. The availability of shares of preferred stock would provide us flexibility in responding to future capital raising, financing and acquisition needs and opportunities without the delay and expense associated with holding a special meeting of stockholders to obtain further stockholder approval. As part of our business and growth strategy, we monitor and screen for potential strategic acquisitions and investments, and shares of preferred stock could be issued on a timely basis as consideration for an acquisition or in connection with the financing of an acquisition or investment. If determined to be in the best interest of SemGroup and its stockholders, the Board of Directors will be able to authorize the issuance of shares of preferred stock without the delay and expense associated with obtaining further stockholder approvals and to customize the terms of the preferred stock to meet the particular needs of any transaction or market conditions.

The Preferred Stock Amendment has been prompted by business and financial considerations. Future purposes for utilizing shares of preferred stock could include, but would not be limited to, issuances in public or private offerings of shares for cash, effecting acquisitions or other strategic transactions, and pursuing additional financing opportunities. We have no current plan, commitment, arrangement, understanding or agreement regarding the issuance of shares of preferred stock resulting from the approval of the Preferred Stock Amendment.

Potential Anti-Takeover Effect of the Proposed Preferred Stock Amendment

The Preferred Stock Amendment is not intended to have any anti-takeover effect and is not part of any series of anti-takeover measures contained in our Amended and Restated Certificate of Incorporation or Amended and Restated Bylaws in effect on the date of this proxy statement. Our Board of Directors represents that, if the Preferred Stock Amendment is approved, it will not, without prior stockholder approval, approve the issuance or use of any of the preferred stock for any defensive or anti-takeover purpose or for the purpose of implementing any stockholder rights plan. Within these limits, as well as others imposed by

applicable law and NYSE rules, our Board of Directors may approve the issuance or use of preferred stock for capital raising, financing and acquisition needs or opportunities that has the effect of making an acquisition of SemGroup more difficult or costly, as could also be the case if our Board of Directors were to issue additional shares of common stock for such purposes.

Effectiveness of the Preferred Stock Amendment

The Preferred Stock Amendment will become effective once it is approved at the Annual Meeting and filed with the Secretary of State of the State of Delaware.

Appraisal Rights

Under Delaware General Corporation Law, stockholders are not entitled to appraisal rights with respect to the proposed Preferred Stock Amendment.

Our Board of Directors recommends a vote “FOR” the approval of the amendment to our Amended and Restated Certificate of Incorporation to authorize 4,000,000 shares of preferred stock.

PRINCIPAL STOCKHOLDERS AND SECURITY OWNERSHIP OF MANAGEMENT

Except as otherwise indicated, we believe that the beneficial owners of our Class A Common Stockstock listed in the tables below, based on information furnished by such owners, have sole investment and voting power with respect to such shares, as the case may be, subject to community property laws where applicable.

Principal Stockholders

The following table contains information regarding the only persons we know of that beneficially own more than 5% of our outstanding shares of Class A Common Stock or Preferred Stock as of March 10, 201729, 2019 (except as noted below). The percentagesPercentage of the Class A Common Stockclass amounts are based on 66,237,00679,531,367 shares of our Class A Common Stock and 350,000 shares of our Preferred Stock outstanding as of March 10, 2017.29, 2019. Percentage of all outstanding voting stock amounts is based on the maximum number of 91,049,975 votes which may be cast at the Annual Meeting if present in person or by proxy, which, as of March 29, 2019, is the sum of (i) outstanding shares of Class A Common Stock and (ii) 11,518,608, which is the number of votes holders of Preferred Stock are entitled to cast at the Annual Meeting.

Stock Ownership of Directors and Executive Officers

The following table sets forth, as of March 10, 2017,29, 2019, the beneficial ownership of our Class A Common Stock by:

None of our directors or executive officers beneficially owns any shares of our Preferred Stock.

Compensation Discussion and Analysis

Executive SummarySummary.. SemGroup is focused on delivering stockholder value through growth and financial discipline. We strive to generate consistent earnings and cash flows and capitalize on growth opportunities around our assets. We are committed to managing risk and promoting a company culture centered on safety and integrity.

This Compensation Discussion and Analysis (“CD&A”) describes SemGroup’s executive compensation program for 2016.2018. Our program is designed to protect our assets in the near-term and position the Company for future growth by attracting, motivating and retaining a senior management team capable of delivering stockholder value by ensuring each of our businesses meet or exceed financial and operational targets. In particular, this CD&A explains how the Compensation Committee of the Board (the “Committee”) made 20162018 compensation decisions for the following named executive officers (“NEOs”):

Our executive compensation program promotes good governance and operates in the best interests of our stockholders. A summary of our compensation governance practices are listed below:

20162018 Business Highlights.During 2016,2018, we successfully implemented several initiatives supporting our strategic plan to grow our presence in the midstream energy sector. We focused on our business objectives, and achieved the following:

20162018 Compensation Decisions & Actions.Actions

20162018 CEO PayAt-A-Glance

The majority of our CEO’s pay is variable and linked to drivers of financial performance or growth in stockholder value. TheTo demonstrate the variable and performance-based nature of CEO compensation, the chart below shows the elements of our CEO’s total direct compensation (base salary, annual bonus, and grant date or target value of annual equity grants) for the past three years. In 2014, Mr. Conner received a one-time equity awardyears, comparing target or grant date value torealizable value at the end of $5 million in shareseach year.

Components of restricted stock and RRMS restricted common units intended in part to make Mr. Conner whole for equity value that he forfeited at his previous employer when he agreed to join SemGroup. This one-time award was also intended to provide immediate and significant direct alignment between Mr. Conner’s compensation and stockholder interests.

Effect of StockholderSay-on-Pay Vote on Executive Compensation Decisions.The Committee has reviewed the voting results from the annual advisory vote on executive compensation (commonly known as asay-on-pay proposal) conducted at our 20162018 annual meeting of stockholders. At this meeting, approximately 98.6%97.7% of the votes cast on thesay-on-pay proposal were in favor of our NEOs’ compensation as disclosed in the proxy statement for that meeting and, as a result, our NEOs’ compensation was approved.

In addition, over the past year we have engaged in a dialogue with many of our stockholders to solicit their input on a range of topics, including executive compensation and governance matters. The Committee determined that, based on such discussions and given the very high level of support, no substantive changes to our executive compensation policies and decisions were necessary. We intend

The Committee continues to continue such dialogue withbelieve that a substantial majority of NEO compensation should be variable, at risk and subject to performance conditions. Given that 80% of CEO compensation and over 65% of compensation for our stockholders,other NEOs remains variable/at risk, we believe our compensation program is designed to drive and reward outstanding performance in the face of these challenging market conditions.

The Committee intends to continue to make its executive compensation decisions as it has in the past year by focusing on performance-based compensation, gauging competitive practices and authorizing compensation that is within the range of what is deemed to be competitive and appropriate in our industry.

The Committee continues to value the opinions of our stockholders. In the event there is any significant vote against the compensation of our NEOs as disclosed in the proxy statement, the Committee will consider the concerns of the stockholders and evaluate any actions necessary to address such concerns.

The Committee continues to believe that a substantial majority of NEO compensation should be variable, at risk and subject to performance conditions. Given that 80% of CEO compensation and over 65% of compensation for our other NEOs is variable/at risk, we believe our compensation program is designed to drive and reward outstanding performance in the face of these challenging market conditions.

Compensation PhilosophyPhilosophy.. Our Committee oversees an executive compensation program designed to motivate high performance, ethics and alignment with the interests of our stockholders. Our compensation program rewards our executive officers for achieving performance objectives and fostering a culture of collaboration and teamwork. This forms the basis of ourpay-for-performance philosophy.

To support our compensation philosophy, we established the following objectives:

We design, implement and administer our compensation program to support our philosophy.

Compensation OverviewOverview.. Consistent with our philosophy, our compensation program consists of a market-competitive pay mix designed to motivate and reward our NEOs for successfully implementing our strategy to grow our business and create long-term stockholder value. We believe dividing the total compensation awarded to executive officers among the following four directthree primary components helps us achieve a balanced set of incentives to accomplish our goals:

program.

Elements of Compensation. Our mixThe primary components of executive compensation includes:are base pay, short-term cash incentives and long-term equity incentives and benefits.incentives. The chart below summarizes how our compensation design supports our compensation objectives:

Emphasis on variable and incentive-based pay.The majority of an executive’s compensation should be based on his or her contribution to the success of the Company and the creation of value for our stockholders. Our executive compensation is heavily weighted toward variable, at risk, pay elements based on performance. To further strengthen our alignment with stockholders, the majority of our executives’ variable, at risk compensation is based on our long-term success.

Compensation Methodology.Setting executive pay is an annual process that involves our management, the Committee, our Audit Committee, our Board of Directors and an independent compensation consultant. We review our pay programs to ensure consistency with our compensation philosophy and business objectives. The Committee strives to target total direct compensation levels to be competitive with the market in which we compete for executive talent.

We review each NEO’s total compensation in light of our Company’s strategic objectives, market conditions and individual responsibilities and accomplishments. Part of this review includes considering the appropriate compensation level and mix. Although we focus on total direct compensation, each individual element of compensation is reviewed against the market, which includes the 25th, 50th and 75th percentile of compensation paid to similarly situated executives represented in the market data, to ensure our compensation is in line with the market. VariationsWe generally target the median of the market, but variations from the median may occur due to experience, skills, criticality of function to the Company and the sustained performance of the executive.

Role of the Board of Directors. The Board of Directors acts on any recommendations regarding executive compensation matters made by the Committee and its independent directors approve CEO compensation.

Role of the Compensation Committee. Under its charter, the Committee is charged with establishing our compensation program and compensation policies, approving and recommending compensation program designs to the full Board for approval. Also, the Committee has the responsibility for recommending the compensation of our CEO to the Board of Directors for approval. For all other NEOs, the Committee reviews the CEO’s recommendations, supporting market data and individual performance assessments in establishing targets under the compensation program, and administering and approving payouts pursuant to such program. The charter authorizes the Committee to engage consultants and other professionals without management approval to the extent necessary. Details of the Committee’s authority and responsibilities are specified in the Committee’s charter, which is available on our website at http://www.semgroupcorp.com.www.semgroup.com.

Role of Management. Our CEO and other executive officers develop recommendations regarding the appropriate level and mix of compensation for their direct reports. Recommendations are based on our compensation philosophy, the range of compensation programs authorized by the Committee, market data from nationally recognized executive and industry related salary surveys, and the individual responsibilities and performance of each direct report.

Our CEO and Vice President of Human Resources provide support to the Committee and attend all Committee meetings, but are not present for discussion of their individual compensation.

Role of Audit Committee. With respect to our Chief Financial Officer (“CFO”), the Audit Committee of the Board of Directors consults with management and the Committee about his performance evaluation and compensation.

Additionally, the Audit Committee validates the calculation of our achievement percentage for each performance measure prior to the determination of our incentive pool. Our internal audit function confirms the short-term incentive pool before payments are processed. Also, the internal audit function validates the calculation of our achievement percentage for our performance metrics related to our performance-based equity awards. Our internal audit function confirms the calculation prior to the Committee certifying the achievement of our performance-based equity awards and distribution of equity awards.

Role of the Independent Compensation Consultant. The Committee engaged Pearl Meyer & Partners (“Pearl Meyer”) to serve as its independent compensation consultant on matters related to executive compensation during 2016,2018, including the review of executive compensation recommendations provided by management. Pearl Meyer also provided guidance on director compensation. Pearl Meyer reported directly to the Committee and performed no other services for the Company. The Committee has assessed the independence of Pearl Meyer pursuant to SEC rules and concluded that Pearl Meyer’s work for the Committee during 2018 did not raise any conflict of interest.

The Committee regularly reviews consultant independence and the services provided by its outside consultant. In making its determination regarding the independence of outside advisors for 2016, the Committee noted that:

The Committee monitors the independence of its compensation consultant on an annual basis.

Role of the Peer Group. The Committee compares our executive compensation program to a group of companies that are comparable in terms of size and industry (“the peer(the “peer group”). The peer group serves two purposes:

•

TSR Performance:Measures our relative TSR performance for purposes of determining a portion of the value of the performance- basedperformance-based awards under our long-term incentive plan. We must achieve an attractive TSR relative to our peer group to deliver a target-level award. Please see “Long-Term Incentives” for more information about performance-based awards.

Pearl Meyer provided the market data used when designing our NEOs’ compensation program for 2016. Pearl Meyer’s market compensation analysis used compensation information from SemGroup’s current peer group as the primary data source. Where there was insufficient data from the peers (e.g., small sample sizes, etc.), the market data was supplemented with data from other similarly- sized companies that operate in the Oil and Gas Storage & Transportation industry and/or Energy sector.

For 2016,2018, the peer group includes the following 1914 companies, which comprise a mix of both direct competitors and companies whose primary business matched at least one of our business groups:

While some of the companies in our peer group have revenues, assets and market capitalization larger than SemGroup, we believe the peer group continues to be aligned with our current organization as well as the strategic vision of our company. The Committee reviews our peer group annually and makes adjustments as necessary. In its review

Role of Market Data.Pearl Meyer provided the market data used when designing our NEOs’ compensation program for 2016,2018. Pearl Meyer’s market compensation analysis used compensation information from SemGroup’s current peer group as the primary data source. Where there was insufficient data from the peers (e.g., small sample sizes, etc.), the market data was supplemented with data from othersimilarly-sized companies that operate in the Oil and Gas Storage & Transportation industry and/or broader Energy sector.

When determining salaries, target bonus opportunities and annual long-term incentive grants for NEOs, the Committee approved several changes to thedoes not rely upon peer group to account for acquisitions, changes in size,data alone but also considers the performance of the Company and the availabilityindividual, the nature of publican individual’s role within the Company, experience in the officer’s current role, as well as input from its independent compensation data.

Salaries for our NEOs were adjusted during 2018 based upon individual merit and a desire to keep pace with changes in market data for these positions.

2018 Weighting of Performance Measures.The weighting of performance measures for our NEOs in 2018 were as follows:

The chart below shows the achievement of our 20162018 performance measures and the resulting recommendedcalculated funding level.