There are several origins suggested for the Clan Macmillan, and the fact that they were found in widley separated areas makes the problem more difficult. Skene suggests that they were connected with the Clan Chattan, and Buchanan of Auchmar claims their descent from the Buchanans. The name Macmillan if of ecclesiastical origin and a like origin is claimed for the name Buchanan, and the armorial bearings of both clans contain a rampant lion.

The Macmillans were in the Loch Arkaig district in the twelfth century when it is alleged they were removed to the crown lands round Loch Tay. About two centuries later they were driven from Lawers, and the greater number settled in Knapdale, while the others travelled farther south and the branch in Galloway is claimed to be of the latter number.

Macmillan of Knap was considered to be the chief of the clan, and when the Knapdale Macmillans became extinct, the chiefship passed to the family of Dunmore, an estate lying on the side of Loch Tarbert opposite Knapdale, but the family is now extinct. The clan is still associated with districts originally in possession of Macmillans as Lochaber, Argyllshire and Galloway.

Crest: A dexter and sinister hand brandishing a two handed sword, proper. Badge: Holly.