Alexander Duff (British Army officer)

General Sir Alexander Duff GCH (1777 – 21 March 1853) was a British Army officer of the Napoleonic era.

Duff was a younger brother of James Duff, 4th Earl Fife. In 1793, he was commissioned an ensign in the 66th Regiment of Foot, and served at Gibraltar, in Flanders, in the East Indies in 1798, and under Baird during the invasion of Egypt.

In 1806, Duff commanded the center column in the attack on Buenos Aires. He was appointed colonel of the 37th Regiment of Foot in 1831, was made GCH in 1834, and was promoted general in 1838. From 1848 until his death he was Lord Lieutenant of Elginshire, and was a deputy lieutenant of Banffshire.

Duff married Anne Stein, by whom he had two sons and two daughters, including James Duff, 5th Earl Fife and George Skene Duff.