7 December 1879 – 27 April 1929
He became politically active in 1908 when he joined the Irish Republican Brotherhood. In 1916, as commandant of the Kerry Brigade of the Irish Volunteers, he made preparations for the landing of arms by Roger Casement. Although he was made aware that Casement was arrested on Easter Saturday and was being held in Tralee, he made no attempt to rescue him from Ballymullen Barracks. District Inspector Kearney (RIC) treated Casement very well and made sure Stack was aware that Casement could have been rescued, yet he refused to act as his orders were to rise later.
Stack was arrested and sentenced to death for his involvement in the Rising, however, this was later commuted to penal servitude for life. He was released under general amnesty in June 1917 and was elected as an abstentionist Sinn Féin Member of Parliament for Kerry West in the 1918 Westminster election, becoming a member of the 1st Dáil. He was automatically elected as an abstentionist member of the House of Commons of Southern Ireland and a member of the 2nd Dáil as a Sinn Féin Teachta Dála for Kerry–Limerick West at the 1921 elections.