Domnall Ua Lochlainn

Domnall Ua Lochlainn (1048–1121), son of Ardgar, became king of Ailech in 1083 as leader of the Cenél nEógain, opening his reign with the traditional inaugural cattle-raid. From 1101 to 1119 he contested the high kingship of Ireland with his great southern rival, Muirchertach Ua Briain of Munster.

His jurists argued that a king who could lead his army through all Ireland unbeaten was high king despite opposition. He died at Derry in 1121, and the northern annals styled him over-king of Ireland.