The 1955 Hawaii R6D-1 crash was an accident involving a Douglas R6D-1 Liftmaster of the United States Navy which crashed into a mountain peak in Hawaii on 22 March 1955, killing all 66 people on board. At the time, it was the worst crash involving any variant of the Douglas DC-6 airliner the second-worst aviation accident in U.S. history, and one of the worst air accidents anywhere in history, and it equaled the 11 August mid-air collision of two United States Air Force C-119G Flying Boxcars over West Germany and the 6 October United Air Lines Flight 409 crash as the deadliest air accident of 1955. It remains the worst air disaster in the history of Hawaii and the deadliest accident involving a heavier-than-air aircraft in the history of United States naval aviation.

United Air Lines Flight 409 was a scheduled flight which originated in New York City, New York. The final flight destination was San Francisco, California, with stops in Chicago, Denver and Salt Lake City. The aircraft operating the service, a Douglas DC-4 propliner, registration N30062, crashed into Medicine Bow Peak, near Laramie, Wyoming, on October 6, 1955, killing all 66 people on board. The victims included five female members of the Mormon Tabernacle Choir and military personnel. At the time, this was the deadliest airline crash in the history of American commercial aviation. Another 66 lives had been lost earlier that year in the March 22 crash in Hawaii of a United States Navy Douglas R6D-1 Liftmaster military transport aircraft, and 66 had also died in the mid-air collision of two United States Air Force C-119G Flying Boxcars over West Germany on August 11, placing the three crashes in a three-way tie as the deadliest aviation incidents in 1955.