John of Islay (1434–1503), Earl of Ross, fourth Lord of the Isles, and Mac Domhnaill, was a pivotal figure in late medieval Scotland: specifically in the struggle for power with James Stewart, James III of Scotland, in the remoter formerly Norse-dominated regions of the kingdom. His defeat in this conflict led to rebellion against John by his illegitimate son Angus Óg, resulting in the defeat of John's fleet at the Battle of Bloody Bay in the early 1480s. Thereafter and until his death in 1503 John remained an inconsequential figure while, until his murder in 1490, Angus continued to dominate the affairs of Clan Donald. In 1493 James IV brought the Lordship of the Isles to an end.

Lord of the Isles or King of the Isles (Scottish Gaelic: Triath nan Eilean or Rìgh Innse Gall) is a title of Scottish nobility with historical roots that go back beyond the Kingdom of Scotland. It began with Somerled in the 12th century and thereafter the title was held by a series of his descendants, the Norse-Gaelic rulers of the Isle of Man and Argyll and the islands of Scotland in the Middle Ages. They wielded sea-power with fleets of galleys (birlinns). Although they were, at times, nominal vassals of the kings of Norway, Ireland, or Scotland, the island chiefs remained functionally independent for many centuries. Their territory included much of Argyll, the Isles of Arran, Bute, Islay, the Isle of Man, Hebrides, Knoydart, Ardnamurchan, and the Kintyre peninsula. At their height they were the greatest landowners and most powerful lords after the kings of England and Scotland.