Domnall Mór Ua Briain was also styled King of Limerick, and claimed the title King of Munster.
He spent most of his adult life fighting against the incursions of Norman invaders. In 1171, he submitted to King Henry II of England at Cashel, but he continued to fight successfully against the Norman incursion into south-west Ireland for many years.
In 1175, having demolished the Cambro-Normans at the Battle of Thurles, he consolidated his power by blinding two of his cousins, Dermot mac Taig Ua Briain and Mathgamain mac Toirdhelbeach Ua Briain, in Limerick.
He was, driven from Thomond by Ua Conchobair, the High King, the same year.
In 1176, he drove the Normans from Limerick.
In 1184, some of his territory was enfeoffed to Philip Braose, Lord Deputy of Ireland in exchange for an understanding that his position as ruler of Thomond would be respected by the Normans.
He is buried in the apse of St. Mary's Cathedral, Limerick; his tomb now covered with a carved sepulchre stone near the church's main altar. According to tradition Donal O'Brien, the King of Thomond, founded the Cathedral of St. Mary on the site of his palace on King's Island, Limerick, the palace itself having been built on the site of an earlier church built at the center of the old Norse settlement in Limerick 
He married Urlachan MacMorrough, the daughter of Dermot MacMorrough, King of Leinster.