The SAAB 21 was a Swedish single seat low-wing monoplane fighter and attack aircraft designed and manufactured by SAAB. It used a relatively unorthodox twin boom fuselage with a pusher engine, giving the aircraft an unusual appearance. Work commenced at SAAB following a Swedish Air Force decision to embark on a major expansion program in preparation for the possibility of being drawn into the Second World War. The company designed a monoplane twin-boom aircraft, powered by a single Daimler-Benz DB 605B engine that was positioned to the rear of the fuselage nacelle, directly behind the pilot, that drove a rear-facing propeller, commonly known as a pusher configuration. This arrangement allowed guns to be carried in the aircraft's nose while providing the pilot with good visibility. To enable the pilot to bail out without hitting the propeller behind them, they adopted an ejection seat.

On 30 July 1943, the 21 performed its maiden flight and on 1 December 1945, the first examples of the J 21A-1 were introduced to service. It was quickly followed by the improved J 21A-2, which featured a heavier armament, and the B 21A-3 fighter-bomber. Due to Swedish Air Force interest in jet fighters, SAAB produced a conversion using the British de Havilland Goblin under the designation Saab 21R. The 21 was replaced in the mid-1950s after less than 10 years of service by the similarly configured de Havilland Vampire and the Saab 29 Tunnan.

Controls:
VTOL: Flaps
Trim: Elevator Trim