Aleksei Aleksandrovich Gubarev (Russian: Алексе́й Алекса́ндрович Гу́барев; 29 March 1931 – 21 February 2015) was a Soviet cosmonaut who flew on two space flights: Soyuz 17 and Soyuz 28.

Umberto Guidoni (born 18 August 1954 in Rome) is an Italian astrophysicist, science writer and a former ESA astronaut, being the first European to visit the International Space Station. He is a veteran of two NASA space shuttle missions.

Jügderdemidiin Gürragchaa, born 5 December 1947) was the first Mongolian in space. He was selected as part of the eighth Intercosmos program on 1 March 1978, at time he was in the rank of Major General. His backup was Maidarjavyn Ganzorig. Gürragchaa, along with Soviet cosmonaut Vladimir Dzhanibekov, departed from Baikonur Cosmodrome on 22 March 1981. They docked with Salyut 6. While in orbit, Dzhanibekov and Gürragchaa carried out experiments on earth science. After 124 orbits and 7 days, 20 hours and 42 minutes in space, Gürragchaa and Dzhanibekov landed 170 km southeast of Dzhezkasgan.

Claudie André-Deshays Haigneré (born 13 May 1957) is a French former astronaut with the Centre National d'Études Spatiales and the European Space Agency. She was the first French woman to go the space and the first European woman to visit the International Space Station.

James Halsell was an Air Force Test Pilot when he was selected by NASA to become an Astronaut in 1990. He was a veteran of five flights totalling over 1,250 hours in space, pilot of two STS missions and commander of three. He also served as a manager for Shuttle Launch Integration and Space Shuttle Program manager. After the Columbia accident he led the NASA Return to Flight Planning team.

Kenneth Todd "Hock" Ham is a retired American astronaut and a captain in the United States Navy. Ham was selected for NASA's astronaut program in August 1998. Ham has served as CAPCOM for Space Shuttle ascent/entry and orbit, as well as the International Space Station (ISS).

Lloyd Blaine Hammond Jr. is a Gulfstream test pilot, a former United States Air Force officer, and a former NASA astronaut. He flew on two Space Shuttle missions. Selected by NASA in May 1984, Hammond became an astronaut in June 1985 and qualified for assignment as a pilot/commander on Space Shuttle flight crews.

Jeremy Roger Hansen is a Canadian astronaut with the Canadian Space Agency (CSA). He was selected to join the CSA in the 2009 CSA selection.

Gregory Jordan Harbaugh is a former NASA astronaut that spent 34 days in space through four Space Shuttle missions including the first . docking missions with the Russian Space Station Mir and the second Hubble Space Telescope servicing mission.

Bernard Anthony Harris Jr. is a former NASA astronaut. On February 9, 1995, Harris became the first African American to perform an extra-vehicular activity (spacewalk), during the second of his two Space Shuttle flights.

Terry Jonathan "T.J." Hart is an American mechanical and electrical engineer, a retired United States Air Force lieutenant colonel and pilot, and former NASA astronaut. Hart was selected as an astronaut candidate by NASA in January 1978. He flew as a mission specialist on STS-41-C and logged a total of 168 hours in space.

Henry Warren "Hank" Hartsfield Jr. was a United States Air Force officer and a USAF and NASA astronaut who logged over 480 hours in space. Hartsfield became a NASA astronaut in September 1969. Hartsfield was the pilot on STS-4, the fourth and final orbital test flight of the shuttle Columbia.