Peggy Annette Whitson (born February 9, 1960) is an American biochemistry researcher, retired NASA astronaut, former NASA Chief Astronaut, and an active Axiom Space astronaut. Whitson has a total of 675 days in space, more than any other American or woman.

Her first space mission was in 2002: an extended stay aboard the International Space Station as a member of Expedition 5. On her second mission, Expedition 16 in 2007-2008, she became the first woman to command the ISS. In 2009, she became the first woman to serve as NASA's Chief Astronaut, the most senior position in the NASA Astronaut Corps. In 2017, Whitson became the first woman to command the International Space Station twice. Her 289-day flight was the longest single space flight by a woman until Christina Koch's 328-day flight.

Whitson holds the records for the oldest woman spacewalker and the most spacewalks by a woman. Whitson's cumulative EVA time is 60 hours, 21 minutes, which places her in fifth place for total EVA time. At age 57 on her final NASA flight, she was the oldest woman ever in space at that time - a record broken in 2021 by Wally Funk. She is still the oldest woman to orbit the Earth, a record she broke in 2023, at 63.

On June 15, 2018, Whitson retired from NASA. She later became a consultant for Axiom Space and is the commander of Axiom Mission 2.