John Blake Rice (born: May 28, 1809; died: December 17, 1874; buried in Rosehill Cemetery) served as mayor of Chicago, Illinois (1865-1869) for the Republican Party.

Rice arrived in Chicago in 1847 to work as an actor and entertain the politicians at the River and Harbor Convention , Chicago's first national convention. He decided to stay and establish a permanent theater, called Rice's Theater . On July 30, 1850, in the middle of the opera La Somnambula , a fire broke out in the theater. Rice addressed the crowds, saying "Sit down. Do you think I would permit a fire to occur in my theater?" The crowd sat, but a prompter stage-whispered to Rice that the theater was on fire and panic ensued. The theater was destroyed and he lost about $4,000. When a benefit only raised $60, he left Chicago for Milwaukee, Wisconsin.

Rice return to Chicago in 1851 and built a new theater, entirely of brick. He hired James McVicker to serve as manager and was active in the theater until 1857.

Near the end of the Civil War, Rice ran for mayor of Chicago as a very conservative Republican. Aided by the end of the war and the subsequent assassination of Abraham Lincoln only days before the election, Rice won easily.

As mayor, Rice was anti-labor, and he vetoed a plan to enforce an eight-hour work day. This veto led to a spontaneous demonstration on May 1, 1867 by workers which led to the international May Day observance. The City Council eventually overrode his veto.

Rice and the City Council were connected with graft, prostitution and gambling, and he was defeated by Roswell B. Mason in 1869.