Gregory Errol Chamitoff is a NASA astronaut. He was assigned to Expedition 17 and flew to the International Space Station on STS-124, launching 31 May 2008. He was in space 184 days, joining Expedition 18 after Expedition 17 left the station, and returned to Earth 30 November 2008 on STS-126.

Chamitoff was born 6 August 1962 in Montreal, Quebec, Canada to a Jewish family of Russian origin and is married to Alison Chantal Caviness, M.D.,M.P.H.,Ph.D., assistant Professor, Department of Pediatrics, Section of Emergency Medicine, Baylor College of Medicine, Houston, Texas . They have two children, Natasha and Dimitri. His mother Shari Chamitoff and brother Ken Chamitoff live in southern California. His father was the late Ashley "Al" Chamitoff. His wife's parents are Madeline Caviness, Ph.D. (as of October 2007 a member of the American Academy of Arts and Sciences), and Verne Caviness, M.D.

Chamitoff's recreational interests include scuba diving, backpacking, flying, skiing, racquetball, Aikido, juggling, magic and guitar. He is a certified divemaster and instrument rated pilot. Chamitoff also enjoys chess and has played games with people on earth while living in the ISS.