Brigadier Ian MacAlister Stewart, 13th Laird of Achnacone, DSO, OBE, MC & Bar, DL (17 October 1895 – 14 March 1987) was a Scottish military officer who served in the British Army during both the First and Second World Wars. Known for his eccentric training methods, he commanded the 2nd Battalion of the Argyll and Sutherland Highlanders, which participated in the Malayan campaign and the Battle of Singapore during the Second World War.