Denis O'Dea (26 April 1905 – 5 November 1978) was an Irish stage and film actor.

He was born in Dublin and attended Synge Street CBS. When very young he and his mother Kathleen (from County Kerry) moved in with her sister, who kept a boarding house at 54 South Richmond Street. He worked in insurance until taking up acting. O'Dea was a leading member of Dublin's Abbey Theatre where he had a great acting career from 1929 to 1953; a list of his performances can be found in the Abbey archives. He also appeared in numerous plays by Irish playwright Teresa Deevy, some of which toured New York and England. His work led to a number of notable film roles, including two mid-1930s John Ford films, The Informer and The Plough and the Stars (1936), and the part of the police inspector in pursuit of IRA man James Mason in Carol Reed's Odd Man Out (1947).