Lieutenant-Colonel Sir Alexander Gordon KCB (1786–1815), was a British Army officer who was killed at the Battle of Waterloo. His correspondence was collated and published early in the early 21st century.
Gordon was the third son of George Gordon, Lord Haddo, son of George Gordon, 3rd Earl of Aberdeen, and Charlotte. His brothers were Prime Minister George Hamilton-Gordon, 4th Earl of Aberdeen, and Sir Robert Gordon. He joined the military campaign against Napoleon during the Battle of Corunna in 1808 as the Aide-de-camp to his uncle, General Sir David Baird, 1st Baronet. He then became ADC to Arthur Wellesley, 1st Duke of Wellington for the next six years, until he was killed at Waterloo.
Gordon received brevet promotions to Major and Lieutenant-Colonel as a reward for carrying to London despatches announcing victory, first at the Battle of Corunna and then at Ciudad Rodrigo. After Bonaparte's exile to Elba in 1814, Gordon was made a KCB. He was mortally wounded at Waterloo while rallying Brunswickers near La Haye Sainte, and died in Wellington's own camp bed in his headquarters during the night.