The Space Shuttle Columbia disaster occurred on February 1, 2003, when the Space Shuttle Columbia disintegrated over Texas during re-entry into the Earth's atmosphere, with the loss of all seven crew members, shortly before it was scheduled to conclude its 28th mission, STS-107.

The loss of Columbia was a result of damage sustained during launch when a piece of foam insulation the size of a small briefcase broke off the Space Shuttle external tank (the main propellant tank) under the aerodynamic forces of launch. The debris struck the leading edge of the left wing (technically, the orbiter struck the debris), damaging the Shuttle's thermal protection system (TPS), which protects it from heat generated with the atmosphere during re-entry. While Columbia was still in orbit, some engineers suspected damage, but NASA managers limited the investigation on the grounds that little could be done even if problems were found.

NASA's Shuttle safety regulations stated that external tank foam shedding and subsequent debris strikes upon the Shuttle itself were safety issues that needed to be resolved before a launch was cleared, but launches were often given the go-ahead as engineers studied the foam shedding problem without a successful resolution. The majority of Shuttle launches recorded such foam strikes and thermal tile scarring in violation of safety regulations. During re-entry of STS-107, the damaged area allowed the hot gases to penetrate and destroy the internal wing structure, eventually causing the in-flight breakup of the vehicle. A massive ground search in parts of Texas, Louisiana and Arkansas recovered crew remains and many vehicle fragments.

Mission STS-107 was the 113th Space Shuttle launch. It had been delayed 18 times over the two years from its original launch date of 11 January 2001 to its actual launch date of 16 January 2003. (It was preceded by STS-113.) A well-publicized launch delay due to cracks in the shuttle's propellant distribution system occurred one month before a 19 July 2002 launch date. The Columbia Accident Investigation Board (CAIB) determined that this delay had nothing to do with the catastrophic failure six months later.

The Columbia Accident Investigation Board's recommendations addressed both technical and organizational issues. The Space Shuttle program was set back over two years by the disaster, a delay comparable only to that resulting from the Challenger disaster. Concurrently, construction of the International Space Station was put on hold, and the station relied entirely on the Russian Federal Space Agency for resupply and crew rotation until STS-114.