Malaysia Airlines Flight 370 (MH370/MAS370) was an international passenger flight operated by Malaysia Airlines that disappeared from radar on 8 March 2014, while flying from Kuala Lumpur International Airport in Malaysia to its planned destination, Beijing Capital International Airport in China. The cause of its disappearance has not been determined. It remains the single deadliest case of aircraft disappearance in history, with all 239 of the plane's occupants killed.

The crew of the Boeing 777-200ER, registered as 9M-MRO, last communicated with air traffic control (ATC) around 38 minutes after takeoff when the flight was over the South China Sea. The aircraft was lost from ATC's secondary surveillance radar screens minutes later but was tracked by the Malaysian military's primary radar system for another hour, deviating westward from its planned flight path, crossing the Malay Peninsula and Andaman Sea. It left radar range 200 nautical miles (370 km; 230 mi) northwest of Penang Island in northwestern Peninsular Malaysia.

With all 227 passengers and 12 crew aboard dead, the disappearance of Flight 370 was the deadliest incident involving a Boeing 777, the deadliest of 2014, and the deadliest in Malaysia Airlines' history until it was surpassed in all three regards by Malaysia Airlines Flight 17, which was shot down by Russian-backed forces while flying over Ukraine four months later on 17 July 2014.

The search for the missing aircraft became the most expensive search in the history of aviation. It focused initially on the South China Sea and Andaman Sea, before a novel analysis of the aircraft's automated communications with an Inmarsat satellite indicated that the plane had travelled far southward over the southern Indian Ocean. The lack of official information in the days immediately after the disappearance prompted fierce criticism from the Chinese public, particularly from relatives of the passengers, as most people on board Flight 370 were of Chinese origin.