Sinn Féin is an Irish republican and democratic socialist political party active in both the Republic of Ireland and Northern Ireland.
The original Sinn Féin organisation was founded in 1905 by Arthur Griffith. Its members founded the revolutionary Irish Republic and its parliament, the First Dáil, and many of them were active in the Irish War of Independence, during which the party was associated with the Irish Republican Army (1919–1922). The party split before the Irish Civil War and again in its aftermath, giving rise to the two traditionally dominant parties of Irish politics: Fianna Fáil, and Cumann na nGaedheal (which merged with smaller groups to form Fine Gael). For several decades the remaining Sinn Féin organisation was small and often without parliamentary representation.