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.

Scottish Gaelic, also known as Scots Gaelic or simply Gaelic, is a Goidelic language native to the Gaels of Scotland. As a Goidelic language, Scottish Gaelic, as well as both Irish and Manx, developed out of Old Irish. It became a distinct spoken language sometime in the 13th century in the Middle Irish period, although a common literary language was shared by the Gaels of both Ireland and Scotland until well into the 17th century. Most of modern Scotland was once Gaelic-speaking, as evidenced especially by Gaelic-language place names.