James J. Lydon, more familiarly known as Jimmy Lydon, born , in Harrington Park, New Jersey, is an American movie actor and television producer, whose career in the entertainment industry began as a teenage actor in the 1930s.

He initially appeared on the Broadway stage in 1937, before making movies beginning as a teenager. One of his first starring roles was the title character in the 1940 movie, Tom Brown's School Days, which also starred Cedric Hardwicke and Freddie Bartholomew. Lydon then starred as the screechy-voiced Henry Aldrich in the movie series of that title, between 1941-1944. He also appeared opposite James Cagney in the 1948 movie, The Time of Your Life. In the 1950s, he had a number of television acting roles, including appearances on Wagon Train and The Twilight Zone. After working increasingly in television in the 1950s, Lydon turned to production roles, helping to create M*A*S*H (1972) and 77 Sunset Strip (1958).

Lydon resides in Bonita, California with his wife, Betty Lou Nedell, whom he married in 1952. They have two daughters.

Born to a large Irish Catholic family (the fifth of nine children) and raised in New York City, Lydon overcame a birth defect and alcoholic father to begin a Broadway career in 1937, acting opposite Van Heflin, Sidney Lumet and Uta Hagen in separate productions. After a number of films with Paramount and RKO, Lydon hit his stride in the "Henry Aldrich" B movie series of the early 1940s. After working increasingly in television in the early 1950s, Lydon turned to production roles, helping to create "M*A*S*H" (1972) and "77 Sunset Strip" (1958). He is still active as a producer and writer.