Eoin O'Duffy (* 28. Januar 1890 in Castleblayney, County Monaghan , Irland; * 30. November 1944 in Dublin), irischer nationalistischer Militärführer und populärkonservativer Chef von Fine Gael („Irish Race“), spielte eine bedeutende Rolle Rolle bei der Entwicklung der irischen Streitkräfte und der Polizei. Seine Unterstützung des Faschismus in den 1930er Jahren kostete ihn jedoch viel von seiner Unterstützung durch die Bevölkerung.
O’Duffy joined the Irish rebels against England in 1917. He became commander of the Irish army (1924–25) after the formation of the Irish Free State (1921) and served as chief commissioner of the Civic Guard (police) from 1922 to 1933. After his removal in 1933 he joined the opposition to Eamon de Valera’s Fianna Fáil government and helped found the Fine Gael party, serving as its president from 1933 until his forced resignation the next year. Head of the fascist Blueshirts from 1933, he lost most of his remaining prestige in an abortive effort to aid Francisco Franco during the Spanish Civil War (1936–39) and died disgraced.