MacDiarmada, Seán (1884–1916)

Irish republican, a leading organizer of the militant Irish Republican Brotherhood (IRB). From 1910 onwards, he edited the movement's newspaper Irish Freedom. He played a major role in preparing the Irish Volunteers for the Easter Rising of 1916. He was executed by the British for his part in the insurrection.

Born in Kiltyclogher, County Leitrim, MacDiarmada campaigned unsuccessfully for Sinn Fein in 1908, but was already actively involved in reviving the moribund IRB. His agents also infiltrated the Gaelic Athletic Association, the Gaelic League, and later the Irish Volunteers.