Bristol Siddeley Engines Limited was formed by a merger of the Bristol Aero-Engines and Armstrong Siddeley Motors. These were the aero engine manufacturing companies of the Bristol Aeroplane Company and the Hawker Siddeley Group.
Armstrong Siddeley Motors had been producing aero-engines and motor-cars since it had been formed in 1919 with the merger of Siddeley-Deasy and the Armstrong Whitworth Company.
Bristol Aero-Engines had been formed in 1920 when the Bristol Aeroplane Company had taken over the assets of the Cosmos Engineering Company.
Bristol Siddeley was bought by Rolls-Royce Limited in 1966 for £63.6 million but retained its own identity and marketing organization for many years as the Rolls Royce Bristol Engine Division.