The 533d Air Defense Group is a disbanded United States Air Force organization. Its last assignment was with the 27th Air Division at Oxnard Air Force Base, California. It was inactivated on 18 August 1955. The group was originally activated as a support unit for the 483d Bombardment Group at the end of World War II in Italy. The group was activated once again in 1953, when ADC established it as the headquarters for a dispersed fighter-interceptor squadron and the medical, maintenance, and administrative squadrons supporting it. It was replaced in 1955 when ADC transferred its mission, equipment, and personnel to the 414th Fighter Group in a project that replaced air defense groups commanding fighter squadrons with fighter groups with distinguished records during World War II.