Donald, Lord of the Isles, was the son and successor of John of Islay, Lord of the Isles and chief of Clan Donald. The Lordship of the Isles was based in and around the Scottish west-coast island of Islay, but under Donald's father had come to include most of the isles and the lands of Somerled, the King of the Isles in the 12th century, Donald's predecessor, including Morvern, Garmoran, Lochaber, Kintyre and Knapdale on the mainland.

John of Islay was the Lord of the Isles (1336–1386) and chief of Clan Donald. In 1336, he styled himself Dominus Insularum, although this was not the first ever recorded instance of the title in use. Some modern historians nevertheless count John as the first of the later medieval Lords of the Isles, although this rather broad Latin style corresponds roughly with the older Gaelic title Rí Innse Gall, in use since the Viking Age. For instance, the even more similar Latin title dominus de Inchegal, applied to Raghnall Mac Somhairle in the mid-12th century. In fact John is actually styled Rí Innsi Gall or King of the Isles shortly after his death in a contemporary entry in the Irish Annals of Ulster. Clan Donald considers the title "Lord of the Isles" to have been in use at least since Angus Mor Macdonald, who died in 1293, and the title "King of the Isles" in use since Somerled, the Norse-Gael who forged the Kingdom of the Isles in the 12th century.