Ó Briain

Ó BRIAIN—I—O'Brian, O'Bryan, O'Bryen, O'Brien, Brien, &c.; 'descendant of Brian.' This family derives its name and descent from Brian Boru, King of Ireland, who was slain at Clontarf, in the year 1014. By his victories over the Danish invaders and their Irish allies, Brian raised his clan, the Ui Toirdealbhaigh, to a position of pre-eminence among the Dalcassians, and laid the foundation of the greatness of his posterity, who became not only the ruling family in Thomond, but one of the most powerful in Ireland. Some of them were kings of Munster, and some of all Ireland. Their possessions included the whole of Co. Clare and large portions of the counties of Limerick, Tipperary and Waterford. They divided into several branches, the principal of which were: the O'Briens of Ara, in the north of Co. Tipperary, whose chief was known as Mac I Bhriain Ara; of Coonagh in the east of Co. Limerick; of Pobelbrien, now the barony of that name in Co. Limerick, whose chief stronghold was Carrigogonnell, on the Shannon; of Aherlow, in Co. Tipperary; and of Cumaragh, in Co. Waterford, who had extensive possessions along the Cummeragh mountains comprising the valley between Dungarvan and the Suir. O'Brien is now one of the most common surnames in Ireland.

Alphabetical Index to Irish Surnames