Once a Thief
- Taon: 1965
- Bansa: France, United States of America
- Genre: Crime, Drama, Thriller
- Studio: Compagnie Internationale de Productions Cinématographiques (CIPRA), Metro-Goldwyn-Mayer
- Keyword: robbery, heist, film noir
- Direktor: Ralph Nelson
- Cast: Alain Delon, Ann-Margret, Van Heflin, Jack Palance, John Davis Chandler, Jeff Corey