Clan MacDonell of Glengarry (Scottish Gaelic: Clann Dòmhnaill Ghlinne Garaidh) is a Scottish clan and is a branch of the larger Clan Donald. The clan takes its name from Glen Garry where the river Garry runs eastwards through Loch Garry to join the Great Glen about 16 miles (25 km) north of Fort William, Highland.

Glengarry is in Lochaber which was part of the ancient Kingdom of Moray that was ruled by the Picts.Ranald was the son of John of Islay, Lord of the Isles, and Ranald himself had five sons. One of them was Alan, the progenitor of the Clan Macdonald of Clanranald and another was Donald. Donald married twice: firstly Laleve, daughter of the chief of Clan MacIver, by who he had one son named John. Donald married secondly a daughter of the chief of the Clan Fraser of Lovat by whom he had two more sons, Alexander and Angus. The first son, John, died without heirs and was therefore succeeded by his half-brother Alexander. Alexander is sometimes considered the first true chief of Glengarry but is usually regarded as the fourth.

Glengarry did not play an important part in the politics of Clan Donald until the late fifteenth century. Traditional rights of the chiefs were being replaced with feudal relationships in which the Crown was the ultimate superior, as part of the royal policy to pacify the Scottish Highlands. Most of the chiefs submitted to James V of Scotland and even the Clan Macdonald of Clanranald accepted charters in 1494. However Alexander of Glengarry did not receive a charter, suggesting that he continued to have a rebellious attitude at this time. Finally in 1531 he submitted to royal authority and was pardoned for past offences. He received a Crown charter on 9 March 1539 for the lands of Glengarry, Morar, half the lands of Loch Alsh, Lochcarron, Loch Broom and also Strome Castle. This did not stop Alexander following Donald Gorm Macdonald of Sleat in trying to reclaim the Lordship of the Isles. Donald Gorm was killed attacking Eilean Donan Castle and the rebellion collapsed.

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