In UFO conspiracy theories, "Hangar 18" is the name given to a building that allegedly contained UFO debris or alien bodies. The name was popularized by conspiracy theorist Robert Spencer Carr in 1974, who claimed the hangar was located at Wright-Patterson Air Force Base near Dayton, Ohio; in actuality, it isn't named Hanger 18, it is Area B, Building 23.
In 1980, a film titled Hangar 18 was released, loosely based on Carr's stories.