A Force of One is a 1979 American martial arts action-thriller film directed by Paul Aaron and starring Chuck Norris, with Jennifer O'Neill, Ron O'Neal, Clu Gulager, and martial artist Bill Wallace in his film debut. Norris plays karate champion Matt Logan, who is hired to assist an anti-narcotics police unit, who are being targeted by a killer. The screenplay by Ernest Tidyman was based on a story co-written by martial artist Pat E. Johnson.

This was the third film to feature Norris as the star, following Breaker! Breaker! (1977) and Good Guys Wear Black (1978). It was released by American Cinema Releasing on May 18, 1979, and received mixed reviews from critics, but was a financial success, grossing nearly five-times its production budget.