The Sikorsky H-19 Chickasaw was one of the first true multi-role helicopters in service in the world and saw extensive service throughout the 1950s and 60s in the service of dozens of countries around the world. Its design was somewhat unconventional, as the engine was housed in the nose through which a diagonal shaft connected the drive to the gearbox. The shaft passed through the cabin (between the two crew) which was located above the cargo hold. Another distinguishing feature was a four-wheel landing gear. In US service, the H-19 was used to fulfill numerous duties including transport, assault (capable of carrying eight fully armed troops), and rescue where it was fitted with a power winch. Some were also used as ASW platforms and others were armed. During the Korean war, the H-19 performed admirably and helped formulate air mobility tactics and battlefield use of helicopters. Aside from the US, the H-19 was license-built by Westland in the UK (where it was known as the Whirlwind and described separately), SNCASE in France and Kawasaki in Japan. However, it was adopted by nearly three dozen countries around the world including many NATO members and other US allies. Some were still active during the Vietnam War but were gradually replaced by the H-34.

The prototype YH-19 (commercial designation S-55) took to the air for the first time on 10 November 1949 and entered service the following year as the H-19A for the USAF. A more powerful engine was fitted on the H-19B and these two were eventually adopted by the US Army as the H-19C and H-19D respectively. Air-sea rescue variants included the SH-19A and SH-19B which were based on their respective USAF versions, as was the HO4S-1. Assault transport versions for the USMC were known as the HRS-1, -2, and -3 and had numerous engine upgrades. After 1962, Army/USAF variants were redesignated UH-19, rescue variants as HH-19 and assault variants as CH-19. British-built versions were known as the Whirlwind and are described separately given their extensive modifications compared to the US originals.