The Battle of Clontarf takes place on Good Friday in 1014 (April 23) between the forces of Brian Boru and the forces led by the King of Leinster, Máel Mórda mac Murchada: composed mainly of his own men, Viking mercenaries from Dublin and the Orkney Islands led by his cousin Sigtrygg, as well as the one rebellious king from the province of Ulster.

It ends in a rout of the Máel Mórda's forces, along with the death of Brian, who is killed by a few Norsemen who are fleeing the battle and stumble upon his tent.

After the battle, Ireland returns to a fractious status quo between the many small, separate kingdoms that have existed for some time.