Denis O'Dea (April 26, 1905 - November 5, 1978) was an Irish stage and film actor, who portrayed Rear Admiral Sir Rodney Leighton in Captain Horatio Hornblower R.N.. He was a leading member of Dublin's Abbey Theatre, where his work led to a number of film roles. He was married to actress Siobhán McKenna from 1956 until his death.