Frank William Dux ( /ˈdjuːks/; born April 6, 1956) is a martial artist, fight choreographer and author. According to Dux, a ninjutsu expert named Senzo Tanaka trained him as a ninja when he was a teenager. He established his own school of ninjutsu called Dux Ryu Ninjutsu, and has said he won a secret martial arts tournament called the Kumite in 1975. His alleged victory at the Kumite served as the inspiration for the 1988 film Bloodsport starring Jean-Claude Van Damme. Dux's victory at the Kumite has been disputed, as has the existence of both the Kumite he described and Senzo Tanaka.
Dux served in the United States Marine Corps Reserve from 1975 to 1981, and claims he was sent on covert missions to Southeast Asia and awarded the Medal of Honor. He also asserts he was recruited by Central Intelligence Agency (CIA) director William J. Casey to work as a covert agent. His military records, however, show he was never sent overseas and has not received any awards; Dux states the military sabotaged his records to discredit him. He has been accused of falsifying his military service by authors B. G. Burkett, Ralph Keyes and Nigel West, and his claim to have worked for the CIA has been dismissed by Director of Central Intelligence Robert Gates, General Norman Schwarzkopf Jr., Major General John K. Singlaub and Soldier of Fortune.