On which mission did the Space Shuttle Columbia break up upon re-entry?

The story behind the answer

Columbia broke apart during re-entry at the end of mission STS-107 on February 1, 2003. Foam insulation shed from the external tank during launch struck the orbiter’s left wing, damaging a reinforced carbon-carbon panel. During re-entry, superheated plasma entered the wing, causing structural failure and the loss of all seven astronauts.

The Columbia Accident Investigation Board grounded the shuttle fleet for over two years and led to major safety changes, including better foam control, on-orbit inspections, and repair procedures. Don’t confuse STS-107 with STS-51-L (Challenger, 1986) or STS-109 (Columbia’s successful Hubble servicing in 2002). Think “107 = early 2000s era” to remember Columbia’s final mission.