James O'Donovan (; 3 November 1896 - 4 June 1979), also known as Seamus or Jim O'Donovan, was a leading volunteer in the Irish Republican Army. He fought in the Irish War of Independence and then on the Anti-Treaty side during the Irish Civil War. He was an explosives expert and was imprisoned a number of times. He is best known for his collaboration with the Abwehr military intelligence of Nazi Germany.