The Kingdom of the Isles, also known as Suðreyjar, was a Norse Viking kingdom based on the Hebrides and the Isle of Man which existed from 855 to 1266. The Vikings sacked the monastery at Iona in 802 and 806, and the Vikings eventually settled on the numerous and sparsely-populated islands off the west coast of Scotland. They called their new kingdom Suðreyjar, the "Southern Isles", to distinguish it from the island kingdoms further north, ruled by their kinsmen. Ivar the Boneless' family ruled over Suðreyjar from 855, sacking the Alt Clut capital of Dumbarton in 870 and launching several raids into Ireland. In 989, the Earl of Orkney Sigurd the Stout conquered Suðreyjar, and it fell to King Aethelred the Unready of Wessex in 1000 before Ragnall mac Gofraid briefly restored Suðreyjar's independence from 1004 to 1005. When Ragnall died in 1005, Sigurd returned to power as King of Suðreyjar, and he was slain at the 1014 Battle of Clontarf in Ireland. By the early 11th century, the Norse settlers of Suðreyjar had adopted Christianity as their faith. In 1099, the Norwegian king Magnus Barefoot conquered Suðreyjar, but Lagmann Godredsson seized power in 1103 and returned Suðreyjar to independence. After the death of Somerled in 1164, the kingdom was divided among his kinsmen, and the kingdom was vassalized by Norway in 1230. It continued to exist until 1266, when, a year after the death of Suðreyjar's last king Magnus Olafsson, Norway formally ceded the Hebrides and the Isle of Man to the Kingdom of Scotland, ending Norway's influence over the islands.
