William H. Gerstenmaier is an aerospace engineer and policymaker who is Vice President of Mission Assurance at SpaceX. He previously served as NASA's Associate Administrator for Human Exploration and Operations between 2005 and July 10, 2019. While in that role, he was described as "arguably the most influential person when it comes to US spaceflight." Prior to being Associate Administrator, Gerstenmaier served as the International Space Station Office Program Manager, at Johnson Space Center, a position he began in June 2002. He spent a total of four decades with NASA.
In February 2020 SpaceX announced that Gerstenmaier had joined the company as a consultant. He was promoted to VP of Mission Assurance one year later.