Career
O'Byrne was elected unopposed as a Sinn Féin Teachta Dála (TD) to the 2nd Dáil at the 1921 elections for the Tipperary Mid, North and South constituency. He opposed the Anglo-Irish Treaty and voted against it. He stood as an anti-Treaty Sinn Féin candidate at the 1922 general election but was not elected.
He was the son of was John O'Byrne of Corville, County Tipperary (who had originally been granted the title of Count by the Pope) and his mother was Eleanor von Hübner, the daughter of Austrian diplomat Count Joseph Alexander Hübner. Patrick O'Byrne married Bernadette Boland in Sneem, County Kerry in 1897. O'Byrne died in 1944 and is buried in St. Cronan's graveyard, Roscrea, County Tipperary.