The dominant Norse-Gaelic dynasty of the Viking Age Irish Sea — the "grandsons of Ívarr," kings of Dublin and repeatedly of York.
The dynasty took its name from Ímar, a Viking leader who with his kinsmen fastened a lasting Norse grip on Dublin in the 850s and 860s; Irish annals call his descendants the Uí Ímair, the "grandsons of Ímar." From Dublin the family ranged across the Irish Sea, raiding and ruling in Ireland, the Hebrides, the Isle of Man, and northern Britain, making themselves the pre-eminent sea-kings of the age.
Their great prize on the British side was York — Jórvík — the rich former Northumbrian capital, which they took in the early tenth century and held intermittently against Wessex.
The dynasty’s history is a long contest for York against the expanding kingdom of Wessex. In 937 Olaf Guthfrithson, king of Dublin, allied with Constantine II of Alba and the Britons of Strathclyde and invaded England, only to be defeated by King Æthelstan at the Battle of Brunanburh — one of the bloodiest battles of the age. Olaf recovered York after Æthelstan’s death in 939, and the family’s kings, including the much-travelled Amlaíb Cuarán, ruled it on and off for another fifteen years.
At York they struck a distinctive coinage bearing the raven, the bird of Odin and the war-standard of the Norse, the emblem by which the dynasty is still remembered.
The Norse kingdom of York was finally extinguished in 954 with the expulsion and death of Erik Bloodaxe, and York passed permanently to the English crown. The Uí Ímair kept Dublin far longer, where they remained a power in Irish and Irish-Sea politics into the eleventh century, until their bloody defeat at Clontarf in 1014 and the rise of new forces reduced them.
Their long dominance shaped the Viking Age around the Irish Sea, and their kings — bridging Ireland, the Isles, and northern England — were among the most far-ranging rulers of early medieval Europe.