The Pegasus was a 9 cylinder one-row radial aircraft engine designed as the follow-on to the Bristol Aeroplane Company's very successful Bristol Jupiter, following lessons learned in the Mercury effort. Confusingly, Bristol chose to reuse the name many years later for the engine used in the Hawker Harrier; that engine later became known as the Rolls-Royce Pegasus.

The Pegasus was the same size, displacement and general steel/aluminium construction as the Jupiter, but other improvements allowed the rpm to be increased from 1950 to 2600 for take-off power. This improved performance considerably from the Jupiter's 580 hp (430 kW), to the first Pegasus II's with 635 hp (474 kW), to 690 hp (515 kW) in the first production model III's, and eventually to the late-model XXII's 1010 hp (750 kW) with improved superchargers (max take-off in all cases).

The most famous use of the Pegasus was on the Fairey Swordfish, and it was also used on the Bristol Bombay. Like the Jupiter before it, the Pegasus was also licensed, but this time only by the PZL company in Poland. They used it on their PZL P.23 and PZL P.37 designs.

Specifications

For Pegasus X:

Bore by stroke: 5.75 by 7.5 in (146 by 191 mm)

Displacement: 1753 in³ (28.7 L)

Compression ratio: (unknown)

Maximum continuous power: 915 hp (682 kW) at 2600 rpm

Take-off power: 960 hp (720 kW) at 2475 rpm

Weight: 1005 lb (456 kg)

Bristol Pegasus is also a motor-racing club in Bristol, England.