BOAC Flight 781 was a scheduled British Overseas Airways Corporation (BOAC) passenger flight from Singapore to London. On 10 January 1954, a de Havilland Comet passenger jet operating the flight suffered an explosive decompression at altitude and crashed, killing all 35 people on board. The aircraft, registered G-ALYP, had taken off shortly before from Ciampino Airport in Rome, en route to Heathrow Airport in London, on the final leg of its flight from Singapore. After it exploded, the debris from the explosion fell into the sea near Elba Island, off the Italian coast.

G-ALYP was the third Comet built. Its loss marked the second in a series of three fatal accidents involving the Comet in less than twelve months, all caused by structural failures; it followed the crash of BOAC Flight 783 near Calcutta, India, in May 1953, and was followed by the loss of South African Airways Flight 201 in April 1954, which crashed in circumstances similar to BOAC 781 after departing from Ciampino Airport.