The Rolls-Royce R was a British aero engine designed and built specifically for air racing purposes by Rolls-Royce Limited. Nineteen R engines were assembled in a limited production run between 1929 and 1931. Developed from the Rolls-Royce Buzzard, it was a 37-litre (2,240 cu in) capacity, supercharged V-12 capable of producing just under 2,800 horsepower (2,090 kW), and weighed 1,640 pounds (770 kg). Factory testing initially revealed mechanical failures that were reduced by the use of redesigned components, greatly improving reliability.
The R was used with great success in the Schneider Trophy seaplane competitions held in England in 1929 and 1931. Shortly after the 1931 competition, an R engine using a special fuel blend powered the winning Supermarine S.6B aircraft to a new airspeed record of over 400 miles per hour (640 km/h). Continuing through the 1930s, both new and used R engines were used to achieve various land and water speed records by such racing personalities as Sir Henry Segrave, Sir Malcolm Campbell and his son Donald, the last record being set in 1939. A final R-powered water speed record attempt by Donald Campbell in 1951 was unsuccessful.
The experience gained by Rolls-Royce and Supermarine designers from the R engine was invaluable in the subsequent development of the Rolls-Royce Merlin engine and the Spitfire. A de-rated R engine, known as the Griffon, was tested in 1933, but it was not directly related to the production Rolls-Royce Griffon of 1939. Three examples of the R engine are on public display in British museums as of 2010.