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On 28 January 1986, the Space Shuttle Challenger broke apart 73 seconds after launching from Kennedy Space Center, killing all seven crew members aboard, including a school teacher from New Hampshire. The spacecraft disintegrated 46,000 feet (14 km) above the Atlantic Ocean near Cape Canaveral, Florida, at 11:39 EST (16:39 UTC). It marked the first fatal accident involving an American spacecraft in flight. In contrast, the fire which claimed the lives of astronauts Chaffee, Grissom and White occurred in a pre-flight test before the Apollo 1 mission in 1967.

The mission, assigned STS-51-L, was the orbiter's tenth flight and 25th of the Space Shuttle fleet. Had the flight achieved orbit, the crew, led by commander Francis R. Scobee, was scheduled to deploy a communications satellite and study Halley's Comet as it passed near the Sun. However, the addition to the crew of Christa McAuliffe, the designated Teacher in Space, garnered higher-than-usual media interest and coverage of the mission; the launch and subsequent disaster were seen live in schools across the United States.

The cause was the failure of the primary and secondary redundant O-ring seals in a joint in the shuttle's right solid rocket booster (SRB). The record-low temperatures on the morning of the launch stiffened the rubber O-rings, reducing their ability to seal the joints. The seals were breached moments after liftoff. Hot pressurised gas from within the SRB leaked through the joint. It burned through the aft attachment strut, which connected it to the external propellant tank (ET) and into the tank. The collapse of the ET's internal structures and rotation of the following SRB threw the shuttle stack, travelling at a speed of Mach 1.92 (2,370 km/h), into a direction that allowed aerodynamic forces to tear the orbiter apart. Both SRBs detached from the now-destroyed ET and flew uncontrolled until the range safety officer (RSO) detonated them.

After a three-month search-and-recovery operation, the crew compartment and other fragments from the Challenger were recovered from the ocean floor. The exact timing of the deaths of the crew is unknown. Still, several crew members are thought to have survived the initial breakup of the spacecraft. The orbiter had no escape system, and the impact of the crew cabin at terminal velocity on the ocean surface was too violent to be survivable.

The tragedy led to a 32-month hiatus in the Space Shuttle program, with President Ronald Reagan creating the Rogers Commission to investigate the accident. The board criticised NASA's organisational culture and decision-making processes that contributed to the accident. Since 1977, test data revealed a potentially fatal flaw in the SRBs O-rings. Neither NASA nor SRB manufacturer Morton Thiokol addressed the issue. NASA managers disregarded engineers' warnings about the dangers of launching in cold temperatures. They did not report these technical concerns to their superiors.

Based on the commission's findings, NASA established the Office of Safety, Reliability, and Quality Assurance and arranged to deploy commercial satellites from expendable launch vehicles rather than a crewed orbiter. To replace Challenger, Congress approved the construction of a new Space Shuttle orbiter, Endeavour, in 1987, and it first flew in 1992. Subsequent missions were launched with redesigned SRBs, and their crews wore pressurised suits during ascent and reentry.