The name Colquhoun is territorial in origin from lands of this name in Dunbartonshire. The clan claim descent from Humphrey de Kilpatrick who received a grant of the lands of Colquhoun from the Earl of Lennox around 1241. His son Ingram is said by tradition to be the first to take the name Colquhoun.

The clan were guardians of the "bachuil" or crozier of St. Kessog, the Martyr who lived on Inchnauannach of Monk's Isle on Loch Lomond. About 1368, Sir Robert Colquhoun of that Ilk married the heiress of Luss and the clan have since that time been known as "of Luss". Sir Robert supported Bruce and fought at Bannockburn. The seat of the clan remains to this day, Rossdhu House, in Luss, on the West Shore of Loch Lomond.

In 1603 a feud between the Colquhouns and Macgregors came to a head at the Battle of Glenfruin, the "Glen of Sorrow", the Colquhouns were massacred and as a result the Macgregors had their name "outlawed" under pain of death. The Macgregor chief was caught through Campbell treachery and hanged with eleven of his principal clansmen.

Sir John, 19th of Luss, was a necromancer and the last known person openly to practise witchcraft in Scotland. He became one of the first Nova Scotia Baronets and married a sister of the Marquis of Montrose. He subsequently fell in love and eloped with another of Montrose's sisters!

Perhaps one of the most remarkable clan chiefs of living memory was the late Sir Iain Colquhoun of Luss. During World War I he killed a Prussian officer with his revolver and 5 Bavarians with an improvised club. Both weapons are now at Rossdhu. Sir Iain was also noted for keeping a fairly tame pet lion in the trenches.

Like many other clansmen, Colquhouns have scattered worldwide and many have found fame. John Caldwell Colhoun 1782-1850 was Vice-President of the United States of America, and a Lieutenant Jimmy Calhoun of the 7th U.S. Cavalry fell fighting the Sioux Indians in Custer's last stand at the Battle of Little Bighorn