William Caldwell (c. 1750 – 20 February 1822), was a Scots-Irish immigrant to North America who became a soldier with the British Indian Department. He fought against the American rebels in the American Revolutionary War, especially with Butler's Rangers, based near upstate New York. After the war, together with other Loyalists, Caldwell was granted land in Upper Canada (now Ontario). He helped found the town of Amherstburg, near the mouth of the Detroit River. He also served as a Lieutenant Colonel in the War of 1812, and from 1814-1815 as the Superintendent of Indians in the Western Department. He was a merchant and farmer in Amherstburg.