Military commander and politician. The son of Thomas Graham, Laird of Balgowan, he was educated by privately. Graham then travelled in Europe before unsuccessfully contesting a parliamentary seat in Perthshire in 1772. In 1774, he married Mary, daughter of Charles Cathcart, the 9th Lord Cathcart (1721-74) who was another military man. The couple settled in the Leicestershire, but spent much of their time in Southern Europe owing to her poor health. In 1787, he bought the small estate of Lynedoch (or Lednock), at Methven.
Graham became actively involved in the military after his wife died in 1792. He organized a regiment of infantry, the 90th Foot (Perthshire Volunteers) and served in Italy (1796), at Messina in conjunction with Nelson, and in 1799 in Malta. He joined Sir Ralph Abercromby's expedition in Egypt in 1801.
He served as Member of Parliament for the county of Perth from 1794 until 1807.
Graham was with General John Moore in Sweden in 1808 and was present at Moore's death at the Battle of Corunna (1809). The same year Graham took part in the disastrous Walcheren expedition in Holland, but returned to Spain in 1810 as a Lieutenant-General. The following year he took the offensive, and won a brilliant action at Barossa. He became second-in-command to Wellington. In 1813, he was a commander at the Battle of Vittoria and took San Sebastian.
He was created a Knight of the Bath (1812) and Baron Lynedoch of Balgowan in 1814. He retired from active service in 1815 and went on to found the United Service Club in London, dabble in politics and travel in Europe. At the age of ninety-two he hurried back from Switzerland to Edinburgh to receive the young Queen Victoria.
At the time of his death (in London) he still served as Governor of Dumbarton Castle. The Lynedoch Monument on the North Inch in Perth commemorates Graham and the regiment he raised (90th Light Infantry - Perthshire Volunteers). His portrait hangs in Perth Museum and Art Gallery.