Ian Duncan Colvin (29 September 1877 — 10 May 1938) was a British journalist and historian.
From 1909 he was a leader writer for The Morning Post. In 1915 he published The Germans in England, 1066–1598 in which he claimed the Hanseatic League tried to control Europe through a mixture of peaceful and violent means.
In 1929 he published his biography of General Reginald Dyer. He also wrote three volumes on the life of the Irish Unionist leader Sir Edward Carson.