Byrne is the first of six children. His father is a cooper and his mother a hospital worker. He is raised Catholic and educated by the Irish Christian Brothers. He spends five years of his childhood in a seminary training to be a Catholic priest. He later says, “I spent five years in the seminary and I suppose it was assumed that you had a vocation. I have realized subsequently that I didn’t have one at all. I don’t believe in God. But I did believe at the time in this notion that you were being called.” He attends University College Dublin (UCD), where he studies archeology and linguistics, and becomes proficient in the Irish language. He plays football in Dublin with the Stella Maris Football Club.
Byrne works in archeology after he leaves UCD but maintains his love of his language, writing Draíocht (Magic), the first drama in Irish on Ireland’s national Irish television station, TG4, in 1996.
He discovers his acting ability as a young adult. Before that he works at several occupations which include being an archaeologist, a cook, a bullfighter, and a Spanish schoolteacher. He begins acting when he is 29 years old. He begins on stage at the Focus Theatre and the Abbey Theatre in Dublin, later joining the Royal Court Theatre and the Royal National Theatre in London.
Byrne comes to prominence on the final season of the Irish television show The Riordans, later starring in the spin-off series, Bracken. He makes his film début in 1981 as Lord Uther Pendragon in John Boorman‘s King Arthur epic, Excalibur.
In November 2004, Byrne is appointed a UNICEF Ireland Ambassador. In 2007 he is presented with the first of the newly created Volta awards at the 5th Jameson Dublin International Film Festival for his lifetime achievement in acting. He also receives the Honorary Patronage of the University Philosophical Society, of Trinity College Dublin on February 20, 2007. He is awarded an honorary degree in late 2007 by the National University of Ireland, Galway, in recognition of his “outstanding contribution to Irish and international film.”
Byrne is featured as therapist Dr. Paul Weston in the critically acclaimed HBO series In Treatment (2008). In his return to theater in 2008, Byrne appears as King Arthur in Alan Lerner and Frederick Loewe‘s Camelot with the New York Philharmonic which is featured in a PBS broadcast in the Live From Lincoln Center series in May of 2008.
(From IMDb Mini Biography by Bernie Corrigan)