​​Armstrong Siddeley started building aero-engines during WWI. Through the 1920s and 30s, they produced a range of air-cooled rotary piston engines. In the 1940s, they were at the forefront of jet engine development and went on to produce a successful range of turbojet and turboprop engines.

Following government intervention, Armstrong Siddeley was merged with Bristol Aero-Engines to form Bristol Siddeley, which was later absorbed into Rolls-Royce. This section covers the engines built by Armstrong Siddeley up to the time it became part of Bristol Siddeley.