The Fairey Gannet is a British carrier-borne aircraft of the post-Second World War era developed for the Royal Navy's Fleet Air Arm (FAA) by the Fairey Aviation Company. It was a mid-wing monoplane with a tricycle undercarriage and a crew of three, and a double turboprop engine driving two contra-rotating propellers.

The Gannet was built in response to the 1945 Admiralty requirement GR.17/45, for which prototypes by Fairey (Type Q or Fairey 17, after the requirement) and Blackburn Aircraft (the Blackburn B-54 / B-88) were built. 

After considering and discounting the Rolls-Royce Tweed turboprop, Fairey selected an engine based on the Armstrong Siddeley Mamba turboprop: the Double Mamba (or "Twin Mamba"), two Mambas mounted side-by-side and coupled through a common gearbox to coaxial contra-rotating propellers. Power was transmitted from each engine by a torsion shaft which was engaged through a series of sun, planet, epicyclic and spur gears to give a suitable reduction ratio and correct propeller-shaft rotation. 

The ASMD.1 engine (2,950 hp/2,200 kW) was used in the Gannet AS.1; ASMD.3 (3,145 hp/2,345 kW) in the AS.4; and ASMD.4 (3,875 hp/2,889 kW) in the AEW.3 variant. The Double Mamba engine could be run with one Mamba stopped to conserve fuel and extend endurance for cruise flight. The contra-rotating propellers meant that when only half of the Double Mamba was running there were no thrust asymmetry problems. The Mamba exhausts were situated on each side of the fuselage, at the root of the wing trailing edge. The gas-turbine engine could run on kerosene, "wide-cut" turbine fuel or diesel fuel, allowing the Admiralty to eliminate the dangerous high-octane petroleum spirit required to operate piston-engined aircraft from carriers.

In 1958 the Gannet was selected to replace the Douglas Skyraider in the AEW role. In order to accommodate the systems required, the Gannet underwent a significant redesign that saw a new version of the Double Mamba installed, new radome mounted under the aircraft, the tailfin increased in area, the undercarriage lengthened and the weapons bay removed. A total of 44 aircraft (plus a single prototype) of the AEW.3 version were produced.