Japan Air Lines Flight 123 was a scheduled domestic passenger flight from Tokyo to Osaka, Japan. On August 12, 1985, the Boeing 747 flying the route suffered a severe structural failure and explosive decompression 12 minutes after takeoff. After flying under minimum control for 32 minutes, the plane crashed in the area of Mount Takamagahara, 100 kilometres (62 mi; 54 nmi) from Tokyo.

The aircraft, featuring a high-density seating configuration, was carrying 524 people. The crash killed all 15 crew members and 505 of the 509 passengers on board, leaving only four survivors. An estimated 20 to 50 passengers survived the initial crash but died from their injuries while awaiting rescue. The crash is the deadliest single-aircraft accident in aviation history and remains the deadliest aviation incident in Japan.

Japan's Aircraft Accident Investigation Commission (AAIC),^: 129 assisted by the U.S. National Transportation Safety Board, concluded that the structural failure was caused by a faulty repair by Boeing technicians following a tailstrike seven years earlier. When the faulty repair eventually failed, it resulted in a rapid decompression that ripped off a large portion of the tail and caused the loss of all hydraulic systems and flight controls.