Clan Lamont (listen^ⓘ; Scottish Gaelic: Clann Laomainn [ˈkʰl̪ˠãũn̪ˠ ˈl̪ˠɯːmɪɲ]) is a Highland Scottish clan. The clan is said to descend from Ánrothán Ua Néill, an Irish prince of the O'Neill dynasty, and through him Niall Noigíallach, High King of Ireland. Clan Ewen of Otter, Clan MacNeil of Barra, Clan Lachlan, and Clan Sweeney are also descendants of Ánrothán. Traditional genealogy would therefore include Clan Lamont among the descendants of Conn Cétchathach.

Clan Lamont ruled most of the Cowal peninsula in Argyll for centuries. However, the clan's standing was damaged by the Dunoon Massacre in 1646, when Campbell clansmen killed around 200 Lamont clansmen. Many Lamonts moved, particularly to the Scottish Lowlands. Today, Lamonts are widespread in Canada, Australia, Britain and other countries.

The 29th and current hereditary chief of Clan Lamont is the Roman Catholic priest Rev. Fr. Peter Lamont, Chief of the Name and Arms of Lamont. Most Lamonts have remained Catholic.

The surname Lamont is derived from Lagman (Lawspeaker) which is from the Old Norse Logmaðr. The Old Norse name Logmaðr is composed to two elements: log which is plural of lag meaning "law" + maðr meaning "man".

Around the year 500, the Irish kingdom of Dal Riata emigrated from Ulster to southwestern Scotland. Based on oral traditions, this invasion into Scottish territory was led by the three sons of Erc, the King of Dal Riata. It was during this "building stage" of the Scottish Kingdom of Dalriada that the Stone of Destiny and the Coronation Stone were brought by the Gaels into Argyll. The Coronation Stone was later brought to Scone, the capital of the Southern Picts. It was there that the Picts and Scots became unified in 844 under the guidance of Kenneth MacAlpine.

Anrothan O'Neill, an Irish prince from the O'Neill dynasty, took advantage of this new Scottish kingdom and gave up his rulership in Ireland to settle down in Argyll. From Anrothan's line came a prominent lord named Aodha Alainn O'Neil, who had three sons: Gillachrist, Neill, and Dunslebhe. Gillachrist's son, Lachlan, founded Clan MacLachlan, and Gillachrist's brother, Neill, founded Clan MacNeil of Barra. Dunslebhe had two sons: Ewen and Fearchar. Ewen founded Clan Ewen of Otter, and Fearchar's grandson founded Clan Lamont.

Until the 13th century, Clan Lamont was known as MacKerracher in honor of Fearchar. In 1235, however, Sir Laumon signed a charter granting lands to Paisley Abbey. From Laumon comes the modern name "Lamont", and the clan became known as such. His descendants, the early chiefs of the clan, were described as "The Great MacLamont of all Cowal" (Scottish Gaelic: Mac Laomain mor Chomhail uile).

During the Wars of Scottish Independence, Sir John Lamont, Laumon's grandson and the Chief of the clan, sided with the MacDougall's of Lorne against Robert the Bruce. The MacDougall bid for the throne was foiled, and the Lamonts suffered along with their allies. Once Robert the Bruce was firmly situated on the throne, he and his line took vengeance against the clans that had opposed him. In 1371, Robert II gave the Lamont hereditary seat at Dunoon to Bruce supporter Sir Colin Campbell, Black Knight of Loch Awe.