The Polikarpov I-15 was a Soviet biplane fighter aircraft of the 1930s. Nicknamed Chaika because of its gulled upper wings, it was operated in large numbers by the Soviet Air Force, and together with the Polikarpov I-16 monoplane, was one of the standard fighters of the Spanish Republicans during the Spanish Civil War, where it was called Chato (snub-nose).

Fighter aircraft are military aircraft designed primarily for air-to-air combat. In military conflict, the role of fighter aircraft is to establish air superiority of the battlespace. Domination of the airspace above a battlefield permits bombers and attack aircraft to engage in tactical and strategic bombing of enemy targets.