The Sikorsky CH-37 Mojave (company designation S-56) is an American large heavy-lift military helicopter of the 1950s. It entered service as the HR2S-1 Deuce with USMC in 1956, and as the H-37A Mojave with the U.S. Army that same year. In the early 1960s the designation was standardized to CH-37 for both services, with the HR2S-1 redesignated as CH-37C specifically.

Developed in the early 1950s with its first flight in 1953, it filled a 1950 Navy requirement for an assault helicopter. The design includes a front loading ramp with side opening clam shell doors on the nose. It is powered by two radial piston engines. It served well into the 1960s in active military service including in Indochina before being replaced, and many ex-military models went onto civilian service in the 1970s. This was the biggest helicopter in the world to enter service at the time, and one of the earliest twin engine models. It was known for being noisy but earned a good reputation for reliability. The Navy also adapted it to carry a naval radar, with two entering service as HR2S-1W.