The 523d Fighter Squadron is an inactive United States Air Force unit. Its last assignment was with the 27th Operations Group stationed at Cannon Air Force Base, New Mexico.

During World War II, its predecessor unit, the 17th Bombardment Squadron (Light) fought in the Philippines campaign (1941–1942). Its ground personnel fought as infantry in the Battle of Bataan with the survivors being forced to march as prisoners in the Bataan Death March. The squadron reformed with its present numerical designation, and by the end of World War II, the Airmen of the 523d were among the most decorated USAAF units of the war, having fought in the North African, Sicilian, Italian and Southern France campaigns in the European Theater.

Until its inactivation in 2007, the 523d had been engaged in every major combat action the United States had engaged in since its activation in 1940 (World War II, both Pacific and European Theaters; Korean War; Vietnam War; Operation Desert Storm; Global War on Terrorism).