STS-1 (Space Transportation System-1) was the first orbital spaceflight of NASA's Space Shuttle program. The first orbiter, Columbia, launched on April 12, 1981, and returned on April 14, 1981, 54.5 hours later, having orbited the Earth 37 times. Columbia carried a crew of two—commander John W. Young and pilot Robert L. Crippen. It was the first American crewed space flight since the Apollo–Soyuz Test Project (ASTP) in 1975. STS-1 was also the maiden test flight of a new American spacecraft to carry a crew, though it was preceded by atmospheric testing (ALT) of the orbiter and ground testing of the Space Shuttle system.
The launch occurred on the 20th anniversary of Vostok 1, the first human spaceflight, performed by Yuri Gagarin for the USSR. This was a coincidence rather than a celebration of the anniversary; a technical problem had prevented STS-1 from launching two days earlier, as was planned.