F-19 is a designation for a United States fighter aircraft that has never been officially used, and has engendered much speculation that it might refer to a type of aircraft whose existence is still classified.
Since the unification of the numbering system in 1962, U.S. fighters have been designated by consecutive numbers, beginning with the F-1 Fury. F-13 was never assigned to a fighter due to superstition, though the designation had previously been used for a reconnaissance version of the B-29. After the F/A-18 Hornet, the next announced aircraft was the F-20 Tigershark. Northrop had requested the "F-20" designation, but the USAF proposed F-19 instead. The USAF finally gave approval for the F-20 designation in 1982. There have been a number of theories put forth to explain this omission, but none have ever been confirmed.
The most prevalent theory in the 1980s was that "F-19" was the designation of the stealth fighter whose development was an open secret in the aerospace community. When the actual aircraft was publicly revealed in 1988, it was called the F-117 Nighthawk. There seems to be no evidence that "F-19" was ever used to designate the Nighthawk, although the National Museum of the United States Air Force website does include the entry "Lockheed F-19 CSIRS (see F-117)" as of 2012.
Another theory suggests that F-19 was the designation applied to the Have Blue technology demonstrator which led to the development of the F-117.
- In the 1983 Chevy Chase film Deal of the Century, Gregory Hines' character "Ray Kasternak" piloted an F-19 in a dogfight against an autonomous drone fighter.
- In 1986, the Testor Corporation released a model aircraft kit, calling it the F-19 Stealth Fighter. 
- Like the Testor Corporation, Monogram models also released the F-19A Specter which was based on the design by Loral Inc
- Jane's Information Group published an incorrect entry on the F-19 in their aviation reference, Jane's All the World's Aircraft 1986-1987. In addition to the fictitious artwork, the 1987-1988 and 1988-89 editions lists the aircraft as the "Lockheed RF-19 and XST". 
- In 1988, Microprose released a computer game entitled F-19 Stealth Fighter, the first computer simulation of stealth air combat.
- The 1990 videogame Air Diver had the similar designated F-119D Stealth Fighter as the main aircraft during gameplay. The designation code F-119 actually refers to the powerplant of the F-22 Raptor currently in use with the United States Air Force.
- The 1990 videogame James Bond 007: The Stealth Affair featured the "F-19" as the captured stealth fighter stolen during a testflight at NAS Miramar that ends up in a fictional Latin American country called Santa Paragua where James Bond is sent to retrieve it.
- In his 1986 novel Red Storm Rising, Tom Clancy featured the "F-19A Ghostrider" (nicknamed "Frisbee" by the pilots and crew) as a secret weapon used to combat a Soviet invasion of Germany. This vehicle was considerably more capable than the F-117, being a supersonic fighter rather than a subsonic precision bomber. The F-19A as described in the book featured underwing hardpoints for various ordnance, including air-to-air missiles and BLU-107 Durandal runway-cratering bombs. The aircraft also has circular wings instead of angular ones, hence the name.