The 1940 Illinois gubernatorial election was held on November 5, 1940.
Before the primary, incumbent governor Henry Horner, a Democrat, opted not to seek a third term. In October, before the general election, his death in office made John Henry Stelle assume the governorship. However, Stelle had previously failed to win the Democratic nomination in the primary.
Republican former Attorney Dwight H. Green won the election, defeating his Democratic opponent, former Mayor of Taylorville Harry B. Hershey, with 52.93% of the vote.