Major Thomas Forsyth (December 5, 1771 – October 29, 1833) was a 19th-century American frontiersman and trader who served as a U.S. Indian agent to the Sauk and Fox during the 1820s and was replaced by Felix St. Vrain, prior to the Black Hawk War.
His writings, both prior to and while an Indian agent, provided an invaluable source of the early Native American history in the Northwest Territory.
Thomas Forsyth and the others were eventually released by Craig, who dropped them off on the riverbank below Alton, Illinois, where they were "in a starving condition (and) they were landed in the woods ... without shelter or food."
He was replaced after 18 years of service by Felix St. Vrain due to Forsyth's insubordinate attitude, unwillingness to remain at the fort, and the criticism of his supervisor.
It has been speculated by historian Lyman Copeland Draper that his removal from the position as Indian agent to the Sauk and Fox could have prevented the Black Hawk War.