Ragnall Ui Imair
Ragnall (Old Norse: Rögnvaldr; Old Irish: Ragnall ua Ímair;died c. 920) was a Norse overlord of northern Britain, including Northumbria, the entire Irish Sea region including the Isle of Man, south to Waterford and briefly much of the Irish province of Munster. At his height he was the most powerful Norse ruler the British Isles had yet seen. Ragnall was one of the grandsons of Ímar, the dynasty known as the Uí Ímair or House of Ivar, along with his contemporary kinsmen Sihtric Cáech and Gofraid.
In 914 Ragnall defeated the fleet of a certain Barid son of Ottir off the Isle of Man. In 917 Ragnall occupied Waterford for a period and raided Munster from it along with Ottir. At the Battle of Corbridge in 918, Ragnall with his kinsman Gofraid, Earl Ottir and Earl Gragabai fought against Constantín II, king of Alba who was assisting Ealdred son of Eadwulf, ruler of Northumbria. The battle was indecisive, but this appears to have been enough to allow Ragnall to establish himself as king at York.
Ragnall died in 921, “king of the fair foreigners and the dark foreigners”. His brother Sihtric succeeded him as king of the Northumbrians at York.