David Stewart was born at Garth Castle on June 1, 1772, the second son of Robert Stewart of Garth, Perthshire, and was descended from James Stewart (grandson of Robert II) who built Garth Castle, north-west of Aberfeldy, as a home for the chieftain of Clan Stewart of Atholl at the end of the fourteenth century. His mother was Janet Stewart, a cousin of his father.

He was given a commission as ensign in the 77th, (Atholl Highlanders) on April 21, 1783, but that regiment was disbanded soon afterwards. He joined the 42nd highlanders (later Black Watch) on Aug. 10, 1787, and became lieutenant on Aug. 8, 1792, and captain-lieutenant on June 24, 1796. He served with the 42nd in Flanders in 1794 during the French Revolutionary Wars under the Duke of York, and went with it to the West Indies in October 1795. As part of the Napoleonic wars, he took part in the capture of the French colonies of St. Lucia and St. Vincent. He was also in the unsuccessful expedition against Porto Rico (Battle of San Juan) in 1797.

Stewart returned to Europe with his regiment, and garrison at Gibraltar. Stewart embarked there with the expedition which resulted in the capture of Minorca in November 1798 (Capture of Minorca (1798)). But he was taken prisoner at sea, and was detained for a total of five months in Spain before he was exchanged. He went to Egypt with Abercromby's expedition ((Egyption expedition)), and was severely wounded at the battle of Alexandria on March 21, 1801. Three months before this, on Dec. 15, 1800, he had obtained a company in the 90th (Perthshire volunteers), but he returned to the 42nd on July 23, 1802.

He obtained a majority in the 78th highlanders, on April 17, 1804, by raising recruits for the second battalion which was then being formed, a thing which his popularity in the highlands made easy to him. His men were so much attached to him that, that when he was at Shorncliffe army barracks, in the following year, Sir John Moore interposed to prevent his being sent to India to join the 1st battalion. He went with the 2nd battalion to the Mediterranean in September 1805, and shared in the descent on Calabria. At Maida, on July 4, 1806, under General John Stuart, he commanded a battalion of light companies and ensuring the defeat of the French under Jean Reynier outside the town. He was again severely wounded. He was appointed lieutenant-colonel of the West India rangers on April 21, 1808, and took part in the capture of Guadaloupe in 1810. He received a medal with one clasp for this and the operation at Maida, and in 1815 he was made C.B. He was promoted colonel in the army on June 4, 1814, and in the following year he was placed on half-pay.

Stewart was later an author and antiquarian, whose book, Sketches of the Character, Manners, and Present State of the Highlanders of Scotland published in two volumes by Archibald Constable and Co in Edinburgh in 1822, was responsible for largely creating the modern image of the Highlander, the clans and Scottish regiments and is considered the foundation for all subsequent work on highlanders, clans and Scottish regiments system.

He died in 1829 in St. Lucia.