Peggy Annette Whitson (born February 9, 1960) is an American biochemistry researcher, NASA astronaut, and former NASA Chief Astronaut. Her first space mission was in 2002, with an extended stay aboard the International Space Station as a member of Expedition 5. Her second mission launched October 10, 2007, as the first female commander of the ISS with Expedition 16. With her two long-duration stays abroad the ISS, Whitson is NASA's most experienced female astronaut, with just over 376 days in space. This also places her twentieth among all space flyers.

The flight of Space Shuttle mission STS-120, commanded by female astronaut Pam Melroy, was the first time that two female mission commanders have been in orbit at the same time.