The Boeing 377, also called the Stratocruiser, was a large long-range airliner built after World War II. It was developed from the C-97 Stratofreighter, a military derivative of the B-29 Superfortress used for troop transport. The Stratocruiser's first flight was on July 8, 1947.

Released in the late 1940s, the aircraft was powered by four piston engines, driving tractor propellers. The aircraft was able to cruise at about 32,000 feet. It also had a pressurized cabin, which was a relatively new feature to transport aircraft at the time, and two decks. Airlines were able to make transoceanic flights easier and faster with the new aircraft, which enabled easier international travel to places such as Hawaii.

Nevertheless, the Stratocruisers did not have great reliability (chiefly due to chronic problems with the extremely complex^{[citation needed]} 28-cylinder R-4360 engines and the associated propellers) and only 56 were built for airlines.

Like the C-97, the 377 was developed towards the end of World War II by adapting an enlarged upper fuselage onto the lower fuselage and wings, which were essentially the same as those of the B-50 Superfortress, the high-performance evolution of the B-29 Superfortress bomber. The 377 was larger and longer-ranged than the Lockheed Constellation and Douglas DC-6, with nonstop transatlantic range eastbound. Production ended in 1950.