The Sikorsky R-5 was the ultimate development of the basic R-4 observation and rescue helicopter that preceded it and was a considerably more radical departure from the original design than the R-6 that was produced concurrently. The R-5 was easily distinguished by an elongated fuselage with a tandem-seat arrangement in which the observer sat in front of the pilot. The main rotor was also considerably larger and powered by a radial engine with over twice the horsepower. Another notable difference was the tricycle landing gear which replaced the earlier tailwheel. The more powerful engines and larger fuselage allowed the R-5 to carry a heavier load than the R-4/6 and therefore made it useful as a utility helicopter for both land- and ship-based roles. As such, it was the first helicopter to operate in the Antarctic and served extensively in the Korean War. It was also license-built in Britain by Westland where it was known as the Dragonfly and served in Malaya. Other users included Argentina, Australia, Canada, China, France and South Africa. The last R-5s were retired from service in the late 1950s when they were replaced by the H-19.

First flight of the prototype XR-5 took place on 18 September 1943 and the first YR-5A was delivered in 1945 for testing. Production versions began with the R-5A which had provision for two stretchers, followed by the R-5D which were the first with a tricycle landing gear, and the R-5F which were based on the civil S-51. After 1948, all of these were redesignated H-6. Further versions included the H-6G four-seater and the updated H-6H, both of which had hydraulic boosted controls and untapered metal blades. Naval versions included the HO2S-1 prototype which was followed by the HO3S-1 four-seater. British versions began with the WS-51 evaluation version followed by the production Dragonfly HR.1, HR.3 and HR.5 for the Royal Navy and HC.2 and HC.4 for the RAF. All of these were fitted with more powerful Leonides engines and were primarily employed on rescue and casevac missions. Additional civilian versions were also built.