Eoin O'Duffy (Irish: Eoin Ó Dubhthaigh; born Owen Duffy, 28 January 1890 – 30 November 1944) was an Irish nationalist political activist, soldier and police commissioner.
He was the leader of the Monaghan Brigade of the Irish Republican Army (IRA) and a prominent figure in the Ulster IRA during the Irish War of Independence.
In this capacity he became Chief of Staff of the IRA in 1922.
He was one of the Irish republicans who along with Michael Collins accepted the Anglo-Irish Treaty and fought as a General in the Irish Civil War on the pro-Treaty side.
O'Duffy became the second Commissioner of the Garda SÃochána, the police force of the new Irish Free State, after the Civic Guard Mutiny and the subsequent resignation of Michael Staines.
He was elected as a Teachta Dála (TD) for Monaghan, his home county, during the 1921 election.
After a split in 1923 he became associated with Cumann na nGaedheal and led the movement known as the Blueshirts.
After the merger of various pro-Treaty factions under the banner of Fine Gael, O'Duffy was the party leader for a short time.
A fascist, O'Duffy was attracted to various fascist movements on the continent.
He raised the Irish Brigade to fight for Francisco Franco during the Spanish Civil War as an act of Catholic solidarity and was inspired by Benito Mussolini's Italy to found the National Corporate Party.
During World War II, he offered to Nazi Germany the prospect of raising an Irish Brigade to participate in the fight against the Soviet Union, but this was not taken up.
O'Duffy was active in multiple sporting bodies, including the GAA and the Irish Olympic Council.