Maryann Mannen

Maryann T. Mannen is an American corporate executive who serves as president, chief executive officer, and chairman of the board of Marathon Petroleum Corporation (NYSE: MPC), the largest petroleum refinery operator in the United States. She became chairman on January 1, 2026, succeeding Michael J. Hennigan, who retired from the position. Mannen leads a Findlay, Ohio-headquartered company with 13 refineries, more than 3 million barrels per calendar day of refining capacity, and an extensive marketing system of branded fuel stations across the United States.

Marathon Petroleum Corporation

Mannen's career has been closely associated with Marathon Petroleum Corporation, one of the largest integrated downstream energy companies in the United States. The company traces its origins to several small oil companies in Ohio that merged in 1887 to form The Ohio Oil Company in Lima, Ohio. It grew significantly over the following decades and, in 2011, was spun off from Marathon Oil Corporation as an independent, publicly traded entity. Marathon Petroleum became the nation's largest petroleum refinery operator through its acquisition of Andeavor on October 1, 2018. The combined company operates 13 refineries across the United States with a total refining capacity exceeding 3 million barrels per calendar day.

Rise to CEO

Mannen rose through the executive ranks of Marathon Petroleum over a career spanning multiple leadership positions within the organization. As CEO, she was responsible for guiding one of the largest publicly traded energy companies in the United States, with operations across the downstream petroleum value chain.

Election as Chairman of the Board

On November 4, 2025, Marathon Petroleum Corporation announced that its board of directors had elected Maryann T. Mannen as chairman of the board, effective January 1, 2026. The announcement was part of a planned leadership transition, with Michael J. Hennigan retiring from the chairman role. Under the new governance structure, John Surma was to continue serving as independent lead director, maintaining the board's independent oversight function alongside Mannen's chairmanship. As chairman and CEO, Mannen assumed responsibility for the strategic direction and governance oversight of a company that operates the largest refining system in the United States.

Board Service at Prudential Financial

Prudential Financial is a global financial services company headquartered in Newark, New Jersey, offering insurance, retirement, and investment management products and services.

Marathon Petroleum Corporation: Company Background

Marathon Petroleum Corporation, the company that Mannen leads, has a corporate history spanning well over a century. Its origins date to 1887, when several small Ohio-based oil companies consolidated to form The Ohio Oil Company in Lima, Ohio. The Ohio Oil Company quickly became the largest oil producer in the state. By 1889, it had been acquired by the Standard Oil Trust, and six years later its headquarters was relocated to Findlay, Ohio, where Marathon Petroleum remains headquartered today. Following the United States Supreme Court's 1911 order to break up Standard Oil under the Sherman Antitrust Act, The Ohio Oil Company again became an independent entity. In 1924, it discovered oil in Texas and acquired Lincoln Oil Refining Company, which included a refinery and 17 brand service stations in Indiana. After the 2011 spinoff, Marathon Petroleum pursued a growth strategy. In 2013 and subsequent years, the company expanded its refining and retail footprint through acquisitions and operational improvements. Its acquisition of Andeavor expanded the company's geographic footprint, adding West Coast refining and marketing operations that had previously been operated under the Andeavor and Tesoro brands. As of 2025, Marathon Petroleum's integrated operations encompass refining and marketing through its direct operations, midstream logistics through its majority-owned subsidiary MPLX LP, and a nationwide network of branded retail fuel stations. The company's common stock trades on the New York Stock Exchange under the ticker symbol MPC, and it is a component of the S&P 500 index.

Recognition

Mannen's election as both chairman and CEO of Marathon Petroleum Corporation placed her at the helm of one of the largest companies in the United States by revenue, as Marathon Petroleum has consistently ranked among the top 50 companies on the Fortune 500 list. The announcement of her chairmanship received coverage in financial and regional news outlets, including those based in the Findlay, Ohio, area where Marathon Petroleum is headquartered. As chairman and CEO of a Fortune 500 company, Mannen is among a small number of women leading major American energy companies, a sector in which female representation at the highest executive levels has historically been limited.

Legacy

Mannen's leadership of Marathon Petroleum Corporation comes at a consequential period for the American petroleum industry, as the energy sector faces evolving market dynamics, regulatory environments, and the broader global conversation about energy transition. As head of the nation's largest refinery operator, her decisions carry implications for fuel supply, employment, and energy policy across the United States. Under a succession of leaders including Mannen, Marathon Petroleum has grown from a regional refining operation into a national petroleum company.