Thomas Cox (1787 – November 9, 1844) was an American pioneer, politician, and surveyor from what is now Kentucky. His family moved to the Indiana Territory, where Cox joined the territory militia. He was promoted to a lieutenant colonel and may have seen service in the War of 1812. After the war, he became a surveyor to help support his family. He also served in county politics until the state of Illinois was formed in 1818. Cox was elected to its 1st General Assembly as a state senator, serving for two years. He then worked as Register of the U.S. Land Office in Springfield, Illinois, but fell into debt after some poor land speculation deals.
Cox served again in the militia near the end of the Black Hawk War, then was appointed a surveyor of the resulting Black Hawk Purchase. He settled in Jackson County and was elected to the Iowa Territory house of representatives for three one-year terms. In 1840, Cox led a posse against a group of outlaws in what would become known as the Bellevue War. Cox was elected to the state assembly as a councilman in 1842 and served one two-year term.