Ms. Mannen is president and chief executive officer of Marathon Petroleum Corporation. She is also president and chief executive officer of MPLX GP LLC.

Ms. Mannen was named president of Marathon Petroleum Corporation in January 2024 and assumed her current role in August 2024. Previously, she served as executive vice president and chief financial officer of Marathon Petroleum Corporation since 2021.

Prior to joining Marathon Petroleum Corporation in 2021, Ms. Mannen served as executive vice president and chief financial officer of TechnipFMC, a leading global engineering services and energy technology company incorporated in the United Kingdom and headquartered in Paris and Houston. From 2011 to 2017, she was chief financial officer at FMC Technologies, prior to its merger with Technip SA, which Ms. Mannen played a key role in negotiating and executing. Before that, she served as the company's deputy chief financial officer and treasurer from 2010 to 2011 and vice president of administration from 2007 to 2010. Prior to joining FMC Technologies in 1986, Ms. Mannen was finance manager for Sheller-Globe Corporation.

Ms. Mannen holds a bachelor's degree in accounting and a Master of Business Administration degree from Rider University.

Ms. Mannen serves on the boards of directors of Marathon Petroleum Corporation and MPLX GP LLC. She is a member of the Owens Corning board of directors, where she has served as the audit committee chair since 2019. She also serves as secretary of the Cynthia Woods Mitchell Pavilion board of directors and is a member of its executive and finance committees.