Mark W. Siegel is an American business executive with extensive experience in the oil and gas industry. He served as President and Chief Executive Officer of Patterson-UTI Energy, Inc., a leading provider of onshore contract drilling and pressure pumping services, from May 2009 until his retirement in May 2017. During his tenure, Siegel oversaw significant growth for the company, including expansions through acquisitions (such as the 2014 combination with UTEX Industries to bolster pressure pumping capabilities) and navigating the volatile energy markets during the shale revolution. Prior to becoming CEO, he joined Patterson-UTI in 1999 as Vice President of Marketing and Business Development, advancing through senior roles such as Executive Vice President and Chief Operating Officer. Before joining Patterson-UTI, Siegel held various engineering and management positions at companies like Halliburton and Dresser Industries, accumulating over 30 years in the sector. His leadership emphasized operational efficiency and strategic mergers, with a focus on onshore operations in key U.S. basins like the Permian and Eagle Ford. Post-retirement, he has remained active in the industry, serving on the board of directors for several energy-related firms and contributing to advisory roles. Siegel is recognized for his contributions to the industry's technological advancements and safety standards, reflecting deep expertise in mechanical engineering applied to energy services.