Tomás Séamus Ó Fiaich, KGCHS was an Irish cardinal of the Catholic Church. He served as the Catholic Primate of All Ireland and Archbishop of Armagh from 1977 until his death. He was created a Cardinal in 1979. Ó Fiaich was born in 1923 in Cullyhanna and raised in Camlough, County Armagh.

The Archbishop of Armagh is an archiepiscopal title which takes its name from the city of Armagh in Northern Ireland. Since the Reformation, there have been parallel apostolic successions to the title: one in the Roman Catholic Church and the other in the Church of Ireland. The archbishop of each denomination also holds the title of Primate of All Ireland.