Tomás Séamus Ó Fiaich (3 November 1923 – 8 May 1990) was an Irish-born prelate of the Roman Catholic Church. He served as the Roman Catholic Archbishop of Armagh and Primate of All Ireland from 1977 until his death. He was created a Cardinal in 1979. He was born in 1923 in Cullyhanna, and raised in Camlough, County Armagh, Northern Ireland, UK.
Tomás Ó Fiaich (sometimes anglicised as Tom or Thomas Fee) was ordained a priest on 6 July 1948; he spent his first year of ordination as assistant priest in Clonfeacle parish. He undertook post-graduate studies in University College, Dublin, (1948–50), receiving an MA in early and medieval Irish history; he also studied at the Catholic University of Leuven, Belgium, (1950–52), receiving a licentiate in historical sciences.
In 1952 he returned to Clonfeacle where he remained as assistant priest till following summer 1953 and his appointment to the faculty of St Patrick's College, Maynooth. Tomás Ó Fiaich was an academic and noted Irish language scholar, folklorist and historian in the Pontifical University in St Patrick's College, Maynooth, the National Seminary of Ireland. From 1959 to 1974 he was Professor of Modern Irish History at the college. In this capacity he suggested to Nollaig Ó Muraíle that he begin research on Dubhaltach Mac Fhirbhisigh and his works. He "was an inspired lecturer, an open and endearing man, who was loved by his students... Tomas O'Fiaich was my Good Samaritan"