A name derived from the district of Buchan which comprises the northeastern part of Aberdeenshire and part of Banffshire. The ancient mormaership, or earldom, of Buchan came into the hands of the Comyns, who were later deprived of it after their defeat at the hands of Robert the Bruce. Buchan was thereafter conferred on Alexander Stewart, the feared Wolf of Badenoch, natural son of Robert II. The geographic name would, however, have been used by notable inhabitants of the district, even although they may have had no provable connection with the great earls.

Black lists Ricardus de Buchan as clerk to the bishopric of Aberdeen around 1207. William de Buchan held land in Aberdeen before 1281. Sir Thomas de Boghan appears on the Ragman Roll rendering homage to Edward I of England in 1296. His lands were around Edinburgh, and his seal bears an eight-rayed figure which may be the derivation of the shining sun which forms part of the chief's crest.

It cannot be accurately ascertained when the Buchans gained the Lands of Auchmacoy, but Andrew Buchan of Achmakwy was one the assize appointed to settle the boundaries of the lands of St. Peter's Hospital in 1446. Auchmacoy seemed to have been in the family's hands from the beginning of the fourteenth century, but it was in 1503 that Andrew, generally reckoned to be the second chief, received a charter to the lands from James IV.

The Barons of Auchmacoy were staunch royalists and from supporters of the Stuarts throughout the seventeenth century. Thomas, the third son of James Buchan of Auchmacoy, was a professional soldier who learned his trade in the wars in France and Holland. He served in Douglas's Scots Regiment, raised for the king of France, until 1686, when he was commissioned colonel in the Earl of Mar's regiment of Jmaes VII. Loyal to his commission, he joined Viscount Dundee to fight for his deposed monarch. After Dundee's death at Killiecrankie in 1689, Buchan was appointed commander-in-chief of all Jacobite forces in Scotland, receiving his commission from the king in Ireland. He returned to Scotland in April 1690 where he met at Keppoch with chiefs sympathetic to the Jacobite cause. It was resolved to delay the general muster of the clans until the summer, but General Buchan was to harry the enemy with his force of twelve hundred foot. On 1 May 1690 at Cromdale, Buchan was taken by surprise by a strong government force under General Mackay. Buchan escaped, regrouped his men, and joined forces with the Farquharsons. The Highland reinforcements encouraged Buchan to take the offensive again. He marched from Abergeldie through the Mearns towards Aberdeen but he was soon opposed by the Master of Forbes and a strong force of cavalry. Buchan cleverly disposed his troops to give an appearance of numerical superiority and his ruse was successful. Forbes retreated towards Aberdeen, causing panic in the city. Buchan, however, had no intention of attacking the city and turned towards Inverness. General Mackay's forces however, marched to intercept him, and Buchan's Highlanders drifted away into their home glens. Buchan was allowed to go into exile in France, but he fought again at the Battle of Sheriffmuir in 1715 and was still in communication with the exiled royal family when he died in 1721.

James Buchan, fourteenth of Auchmacoy, was recognised by the Lord Lyon as chief of the name in April 1830. The title then passed through his only daughter, Louisa, to her cousin, Sir Norman Sinclair, eighteenth Earl of Caithness. He petitioned the Lyon Court in April 1913, taking the surname and arms of Buchan of Auchmacoy. His daughter, Lady Lucy Buchan, married Sir Thomas Innes of Learney, the great Lord Lyon, in 1928. She was the mother of Sir Thomas's younger son, the present Lord Lyon, Sir Malcolm Innes of Edengight. The earl's eldest daughter, Lady Olivia, became the seventeenth of Auchmacoy. Her son changed his name in 1949 to be recognised by the Lord Lyon as chief of the Buchans. The chief's seat remains at Auchmacoy House near Ellon.

Alexander Buchan was an eminent British meteorologist who first observed what were to become known as Buchan spells: departures from the normally expected temperature occuring during certain seasons. Buchan established the weather map as the basis for weather forecasting. John Buchan, born in August 1875, was a clergyman's son, educated at the Universities of Glasgow and Oxford before being called to the Bar in 1901. He served in the colonial service in South Africa and this inspired his literary career. His most famous work was The Thirty-nine Steps, popularised by the motion picture directed by Alfred Hitchcock. In 1935 he was appointed Governor General of Canada and was created first Baron Tweedsmuir.

(Way of Plean, George, and Romilly Squire. 1994. Scottish Clan and Family Encyclopedia. Glasgow, Scotland: HarperCollins Press.)