O’Hanrahan was born in New Ross on 17 March 1877. He was educated by the Christian Brothers in Carlow, and later at Carlow College Academy. He became an active member of the Gaelic League, and founded the first Carlow branch in 1899 and became the secretary. He wrote many articles for republican newspapers, and published two novels, one entitled ‘A Swordsman of the Brigade’, and ‘When the Norman Came’ He was a member of the IRB, and joined the Irish Volunteers in 1913, where he became quartermaster general at headquarters, and went on to become second in command of the 2nd Dublin battalion under Commandant Thomas McDonagh. He fought at Jacob’s Biscuit factory in Dublin. He was captured by British forces, and was executed by firing squad at Kilmainham jail on 4 May 1916. The railway station in Wexford town is named after O’Hanrahan, as well as the main bridge, and local GAA club in the town of New Ross.