In the 1921 Canadian federal election, the Union government that had governed Canada through the First World War was defeated and replaced by a Liberal government under the young leader William Lyon Mackenzie King. A new third party, the Progressive Party of Canada, won the second most seats in the election.

Since the 1911 election, the country had been governed by the Conservatives, first under the leadership of Robert Borden, and then under Arthur Meighen. During the war, the Conservatives had united with the pro-conscription Liberal Unionists and formed a Union government. A number of MPs, mostly Quebecers, stayed loyal to Sir Wilfrid Laurier, however, and maintained their independence. When Laurier died, he was replaced as leader by the Ontarian Mackenzie King. After the 1919 federal budget, a number of western unionist MPs, who were former Liberals, left the Union government in protest against high tariffs imposed by the budget. Led by Thomas Alexander Crerar, this group became known as the Progressive Party. Also running were a number of Labour advocates, foremost amongst them J. S. Woodsworth of Winnipeg.

Meighen attempted to make the "Unionist" party a permanent alliance of Tories and Liberals by renaming it the National Liberal and Conservatve Party but this name change failed and most Unionist Liberals either returned to the Liberal fold or joined the new Progressive Party. The Conscription Crisis of 1917 had a lasting effect on Tory fortunes by making the party virtually unelectable in Quebec.

The election was the first one in which the majority of Canadian women were allowed to vote. Four women also ran for office. Agnes Macphail of the Progressive Party was elected as the first woman MP in Canada.

Parliament was split three ways by this election. King's Liberals ended up one seat short of a majority government: they won almost all of Quebec, much of the Maritimes, and a good portion of Ontario. The Progressive Party won the second largest number of seats, dominating the West, and winning almost a third of the seats in Ontario. The party won only one seat east of Ontario, however. Despite winning the second most seats, they declined to form the official opposition.

The Conservatives won only a few fewer seats than the Progressives and formed the official opposition. They also won a good section of Ontario and had some support in the Maritimes and British Columbia.

Two Independent Labour MPs were elected: J. S. Woodsworth won his seat, largely due to his role in the 1919 Winnipeg General Strike, and William Irvine was elected in Calgary.

National results

Notes:

"Previous" refers to the results from the previous election, and not to the standings in the House of Commons at dissolution.

n.a. = not applicable - the party was not recognized in the previous election

Results by province