A tail gunner or rear gunner is a crewman on a military aircraft who functions as a gunner defending against enemy fighter or interceptor attacks from the rear, or "tail", of the plane.

The tail gunner operates a flexible machine gun or autocannon emplacement in the tail end of the aircraft with an unobstructed view toward the rear of the aircraft. While the term tail gunner is usually associated with a crewman inside a gun turret, the first tail guns were operated from open apertures within the aircraft's fuselage, such as the Scarff ring mechanism used in the British Handley Page V/1500, which was introduced during latter months of the First World War. Increasingly capable tail gunner positions were developed during the interwar period and the Second World War, resulting in the emergence of the powered turret and fire control systems incorporating radar guidance. In particularly advanced tail gunner arrangements, the tail armament may be operated by remote control from another part of the aircraft, such as the American Boeing B-52 Stratofortress, a strategic bomber first introduced during 1955.