The Bristol Pegasus is a British nine-cylinder, single-row, air-cooled radial aero engine. Designed by Roy Fedden of the Bristol Aeroplane Company, it was used to power both civil and military aircraft of the 1930s and 1940s. Developed from the earlier Mercury and Jupiter engines, later variants could produce 1,000 horsepower from its capacity of 1,750 cubic inches by use of a geared supercharger.

Sir Alfred Hubert Roy Fedden MBE, FRAeS was an engineer who designed most of Bristol Engine Company's successful piston aircraft engine designs.