The Norse-Gaels were a cultural group of people descended from Viking settlers in Ireland and Scotland who intermarried with the local Gaelic inhabitants during the early Middle Ages. The Norse-Gaels dominated much of the Irish Sea and Scottish Sea regions from the 9th to 12th centuries. They would found the Kingdom of the Isles, the Kingdom of Dublin and the Lordship of Galloway while a Norse-Gaelic family ruled the Kingdom of York from 939 CE until 943. The most powerful Norse-Gaelic dynasty was Uí Ímair, which controlled much of the Irish Sea, Dublin, the western coast of Scotland and some parts of northern England during the late 9th century. The Raven Clan jarlskona Eivor Varinsdottir was a distant relative of the Norse-Gaelic High King Bárid mac Ímair through the latter's relation to her mother Rosta.
Over time, the Norse-Gaels disappeared as a distinct ethnic group and became Gaelicised. However, they left a lasting influence on Irish and Scottish cultures such as the place names of the Isle of Man and Outer Hebrides to several clans having Norse-Gaelic roots, such as Clan MacDonald, Clan MacDougall and Clan MacLeod. Additionally, the gallowglass emerged from these Norse-Gaelic clans and became a vital part of Irish warfare.