Buchanan of Auchmar traces the origin of the clan to Anselan O Kyan, son of a king of Ulster, who landed in Argyll about the year 1016. For his services against the Danes he received from King Malcolm II the lands of Buchanan, lying to the east of Loch Lomond. These lands remained in the possession of the family for almost seven centuries until the death of John, 22nd laird of Buchanan, in 1682.

Cadets of the clan included the Buchanans of Auchmar, Spittal, Arnprior, Drumikill, Carbeth and Leny, and the chiefship passed ultimately to the Leny branch.

The clan bore their full share of the military operations of their country. They supported Robert the Bruce in his struggle for Scottish independence and the clan was represented in the 7000 men sent from Scotland to assist the French king after the Battle of Agincourt. It is claimed that Sir Alexander Buchanan killed the Duke of Clarence at the Battle of Baugé in 1421. The chief of the clan and Buchanan of Leny fell at Flodden in 1513. The clan took an active part in the Battles of Pinkie and Langside.

George Buchanan, the famous Latin scholar, was born at Killearn in 1506. Educated at St Andrews and Paris, he was imprisoned at the instance of Cardinal Beaton, but escaped to France. He acted as tutor to Mary Queen of Scots, and was afterwards moderator of the General Assembly, and tutor to James VI. From 1570 till 1578 he was Keeper of the Privy Seal. His Latin history of Scotland, and his Latin poetry earned for him European fame. He died in 1582.

Crest: A hand couped, holding a ducal cap, within two laurel branches disposed orlewise, proper. Badge: Bilberry, Oak.
Warcry: Clar Innis (an island on Loch Lomond).

There is a Buchanan Society with headquarters in Glasgow.