King of Munster 1063–86. Toirrdelbach succeeded in restoring the Uí Briain (see dál cais) dynasty to the political dominance it had enjoyed during the reign of his grandfather Brian Bóruma (Boru). Having wrested control of Munster from his uncle Donnchad, with the aid of his ally Diarmait mac Máel na mBó, he sought to assert his authority in Leinster on Diarmait's death in 1072. Subsequently, he marched on Dublin and installed his son Muirchertach Ua Briain as ruler there. Assertion of control in Connacht and in the midland territory of Mide proved more difficult owing to continuous opposition on the part of the Uí Chonchobair (O'Connors) and Uí Ruairc (O'Rourkes). Nevertheless, for much of his reign, Toirdelbach's dominance over the southern half of Ireland was secure. Reflecting this he is termed rí Érenn (king of Ireland) in his death notice in the Annals of Ulster.
From The Oxford Companion to Irish History in Oxford Reference.
Subjects: European History.