The 518th Fighter-Interceptor Squadron is an inactive United States Air Force unit. Its last assignment was with Air Defense Command's 408th Fighter Group at Klamath Falls Airport, Oregon, where it was inactivated on 1 July 1959. The squadron was first activated during World War II as a dive bomber unit, but was disbanded before participating in combat in a general reorganization of Army Air Forces training units. It was reconstituted during the Cold War as a fighter interceptor unit supporting the air defense of the United States.