The Sukhoi Su-27 (Russian: Сухой Су-27) (NATO reporting name: Flanker) is a twin-engine supermanoeuverable fighter aircraft designed by Sukhoi. It was intended as a direct competitor for the large United States fourth generation fighters, with 3,530-kilometre (1,910 nmi) range, heavy armament, sophisticated avionics and high manoeuvrability. The Su-27 most often flies air superiority missions, but is able to perform almost all combat operations. Complementing the smaller MiG-29, the Su-27's closest US counterpart is the F-15 Eagle.

There are several related developments of the Su-27 design. The Su-30 is a two-seat, dual-role fighter for all-weather, air-to-air and air-to-surface deep interdiction missions. The Su-33 ‘Flanker-D’ is a navy fleet defence interceptor for use on aircraft carriers. Further versions include the side-by-side 2-seat Su-34 ‘Fullback’ strike variant and the Su-35 ‘Flanker-E’ improved air defence fighter.