Thomas Dyer (January 13, 1805 – June 6, 1862; buried in Connecticut) served as mayor of Chicago, Illinois (1856–1857) for the Democratic Party.
He also served as the founding president of the Chicago Board of Trade.
He was a former meat-packing partner of former mayor John Putnam Chapin, who was one of Chicago's first meat packers.
Chapin built a slaughterhouse on the South Branch of the Chicago River in 1844.Running as a "pro-Nebraska" Democrat (aligned with Stephen A.
Douglas, who publicly backed his candidacy), Dyer won the contentious 1856 Chicago mayoral election, defeating former mayor Francis Cornwall Sherman (who ran as an anti-Nebraska candidate).