Johnny Sheffield (born John Matthew Sheffield Cassan) was an American child, teen, and young-adult actor, his screen career lasting from 1938 to 1955.

In 1938, Sheffield became a child star after he was cast in the juvenile lead of a West Coast production of the highly successful Broadway play On Borrowed Time, which starred Dudley Digges and featured Victor Moore as Gramps. Sheffield played the role of Pud, a long role for a child. He later went to New York as a replacement and performed the role on Broadway. The following year, his father read an article in The Hollywood Reporter that asked, "Have you a Tarzan Jr. in your backyard?" He believed he did and set up an interview. MGM was searching for a suitable youngster to play the adopted son of Tarzan in its next jungle movie with stars Johnny Weissmuller and Maureen O'Sullivan. When he was 5 years old, Sheffield was taken to an audition where Weissmuller chose him over more than 300 juvenile actors interviewed for the part of "Boy" in Tarzan Finds a Son. In that same year, Sheffield appeared in the Busby Berkeley movie musical Babes in Arms with Mickey Rooney and Judy Garland, classmates of his at the studio school.