Caoimhghín Ó Caoláin (Irish pronunciation: [ˈkiːvʲiːnʲ oː ˈkiːlˠaːnʲ]; born 18 September 1953) is a former Irish Sinn Féin politician who served as a Teachta Dála (TD) for the Cavan–Monaghan constituency from 1997 to 2020. Ó Caoláin's victory in 1997 made him the first member of Sinn Féin to be elected to the Dáil since 1957, and the first to actually take their seat since 1922. His election, which paralleled the signing of the Good Friday Agreement in 1998, is cited as the beginning of Sinn Féin's involvement in the formal national politics of the Republic of Ireland.