Duncan Mackinnon (29 September 1887 – 9 October 1917) was a British rower who competed in the 1908 Summer Olympics.

[1] Mackinnon was born in Paddington, London, and was educated at Rugby School and Magdalen College, Oxford.

[2] The Magdalen crew was chosen to represent Great Britain rowing at the 1908 Summer Olympics, and Mackinnon was in the four with Collier Cudmore, John Somers-Smith and James Angus Gillan.

He returned to England on the outbreak of World War I and was commissioned into the Royal North Devon Hussars.

[5] Mackinnon left a legacy of £80,000 to establish scholarships at Magdalen College, which became effective by reversion in 1938.