born 941, near Killaloe, Ire.
died April 23, 1014, Clontarf, near Dublin
High king of Ireland (1002–14).
He became king of Munster in 976, won control of the southern half of Ireland from the high king Maelsechlainn in 997, and replaced him in 1002. Leinster and the Norsemen of Dublin united against him in 1013 with help from abroad; at the Battle of Clontarf, won by his son Murchad, Brian was killed in his tent by fleeing Norsemen (see Vikings ). A line of princes, the O'Briens, descended from him.