The Space Shuttle Columbia disaster was a fatal incident in the United States space program that occurred on February 1, 2003, when the Space Shuttle Columbia (OV-102) disintegrated as it reentered the atmosphere, killing all seven crew members. The disaster was the second of two fatal accidents in the Space Shuttle program, after the 1986 breakup of Challenger soon after liftoff.

During the STS-107 launch, a piece of the insulative foam broke off from the Space Shuttle external tank and struck the thermal protection system tiles on the orbiter's left wing. Similar foam shedding had occurred during previous Space Shuttle launches, causing damage that ranged from minor to nearly catastrophic,:121 but some engineers suspected that the damage to Columbia was more serious. Before reentry, NASA managers had limited the investigation, reasoning that the crew could not have fixed the problem if it had been confirmed. When Columbia reentered the atmosphere of Earth, the damage allowed hot atmospheric gases to penetrate the heat shield and destroy the internal wing structure, which caused the orbiter to become unstable and break apart.After the disaster, Space Shuttle flight operations were suspended for more than two years, as they had been after the Challenger disaster. Construction of the International Space Station (ISS) was put on hold; the station relied entirely on the Russian Roscosmos State Space Corporation for resupply for 29 months until Shuttle flights resumed with STS-114 and for crew rotation for 41 months until STS-121.

NASA made several technical and organizational changes to subsequent missions, including adding a thorough on-orbit inspection to determine how well the orbiter's thermal protection system (TPS) had endured the ascent, and keeping a designated rescue mission ready in case irreparable damage was found. Except for one final mission to repair the Hubble Space Telescope, subsequent Space Shuttle missions were flown only to the ISS to allow the crew to use it as a haven if damage to the orbiter prevented safe reentry.

The Space Shuttle program was the fourth human spaceflight program carried out by the U.S. National Aeronautics and Space Administration (NASA), which accomplished routine transportation for Earth-to-orbit crew and cargo from 1981 to 2011. Its official name, Space Transportation System (STS), was taken from a 1969 plan for a system of reusable spacecraft of which it was the only item funded for development.The Space Shuttle—composed of an orbiter launched with two reusable solid rocket boosters and a disposable external fuel tank—carried up to eight astronauts and up to 50,000 lb (23,000 kg) of payload into low Earth orbit (LEO). When its mission was complete, the orbiter would reenter the Earth's atmosphere and land like a glider at either the Kennedy Space Center or Edwards Air Force Base.

The Shuttle is the only winged crewed spacecraft to have achieved orbit and landing, and the first reusable crewed space vehicle that has made multiple flights into orbit. Its missions involved carrying large payloads to various orbits including the International Space Station (ISS), providing crew rotation for the space station, and performing service missions on the Hubble Space Telescope. The orbiter also recovered satellites and other payloads (e.g., from the ISS) from orbit and returned them to Earth, though its use in this capacity was rare. Each vehicle was designed with a projected lifespan of 100 launches, or 10 years' operational life. Original selling points on the shuttles were over 150 launches over a 15-year operational span with a 'launch per month' expected at the peak of the program, but extensive delays in the development of the International Space Station never created such a peak demand for frequent flights.