Jacques Joseph O'Mahoney, known professionally as Jock Mahoney, was an American actor and stuntman. He starred in two Western television series, The Range Rider and Yancy Derringer. He played Tarzan in two feature films and was associated in various capacities with several other Tarzan productions. He was sometimes credited as Jack O'Mahoney or Jock O'Mahoney.

Jock entered the University of Iowa in Iowa City and excelled at swimming and diving, but dropped out to enlist in the United States Marine Corps when World War II began. He served as a pilot, flight instructor, and war correspondent. After his discharge from the Marine Corps, Mahoney moved to Los Angeles, and for a time was a horse breeder. However, he soon became a movie stuntman, doubling for Gregory Peck, Errol Flynn, and John Wayne. Most of Mahoney's films of the late 1940s and early 1950s were produced by Columbia Pictures. Like many Columbia contract players, Mahoney worked in the studio's two-reel comedies. Beginning in 1947, he starred with the Three Stooges in their films Out West, Squareheads of the Round Table (and its remake, Knutzy Knights), Fuelin' Around, and Punchy Cowpunchers.