an Irish political party founded in 1905 that united nationalists from the petite and middle bourgeoisie and the radical intelligentsia. The party advocated the emancipation of Ireland from English colonial supremacy.
In 1919, after the party won 73 of the 105 Irish seats in the British Parliament, the Sinn Feiners met in Dublin and formed an Irish parliament (Dáil), which proceeded to proclaim Ireland’s independence. Subsequently independence was achieved through the compromise Anglo-Irish Treaty of 1921. The right-wing leaders of the Sinn Fein concluded the treaty, which led to a split in the Irish national liberation movement and to the civil war of 1922–23. After being defeated in the war, many of the Sinn Feiners, refusing to acknowledge the treaty, went underground.
It was not until the 1950’s that the Sinn Feiners reentered the political arena, reconstructing a party that promoted an anti-imperialistic program for the unification of Ireland. In the early 1970’s the party split into the official wing, which favors the reunification of Ireland by political means, and the provisional wing, which adheres to methods of armed terrorism. In January 1977 the official wing adopted the name Sinn Fein Workers’ Party.