The 1919 Ontario general election, held on October 20, 1919, elected 111 Members of the 15th Legislative Assembly of Ontario ("MLAs"). The United Farmers of Ontario captured the most seats but won only a minority of the legislature. They joined with 11 Labour MPPs and three others to form a coalition government, ending the 14-year rule of Ontario's Conservatives. This is one of the few examples of coalition government in Canadian history.

Premier William Howard Hearst had aimed to win a fifth consecutive term for the Conservatives, but instead the party became the first in Ontario history to fall from first to third place. As newspaperman John Willison later remarked, "There could not have been a worse time for a general election."

The parties tended to have a targeted approach in fielding their candidates:

Toronto was divided into four districts, each with two seats and two separate contests.

Toronto Northeast A saw a Conservative elected by acclamation. Toronto Northeast B saw a four-way fight. Toronto Northwest saw two two-candidate fights. Toronto Southeast had two two-candidate fights. The Toronto Southwest A contest was a two-candidate fight. Toronto Southeast B saw a three-way fight.

Acclamation victories occurred in the Toronto Northeast A contest, as well as in the Addington, Hasting North and Kingston contests.

It was the first election in which women could vote and run for office. Election day was also held on the same day as the scheduled referendum on prohibition.

Hearst alienated the business community with his progressive policies; he had a rift with Adam Beck (London) over the direction of the Ontario Hydro-Electric Commission; and his promotion of prohibition alienated the urban "wets".