Zadok Casey (March 7, 1796 – September 4, 1862) was an American politician who served as a U.S. Representative from Illinois from 1833 to 1843. He founded the city of Mount Vernon around 1817. He was elected to the Illinois House of Representatives in 1822 and to the Illinois State Senate in 1826, and was elected the fourth Lieutenant Governor in 1830. He served in the Twenty-third United States Congress (1833) through the Twenty-seventh United States Congress (1843).