Brian, also called Brian Boru, (born 941, near Killaloe, Ireland—died April 23, 1014, Clontarf, near Dublin), high king of Ireland from 1002 to 1014. His fame was so great that the princes descended from him, the O’Briens, subsequently ranked as one of the chief dynastic families of the country. In 976 Brian became king of a small state, later called Dál Cais, and also king of Munster …

https://www.britannica.com/biography/Brian