Her Majesty's official opposition in Canada is usually the largest political party or coalition which is not a member of the government. This is usually the second-largest party in a legislative house, although in certain unusual circumstances it may be a third or fourth party.

The current official opposition is the Conservative Party of Canada.

They are viewed as the party tasked with keeping the government in check. They are also generally viewed as the alternative government. The Official Opposition maintains a shadow cabinet of MPs that have the same portfolios as actual ministers.

There are some official benefits to being official oppostion. It is the party that gets to speak first after the government, and gets more time in question period than any other party. It also gets more funding for research and staff than other parties.

From 1921 to 1924 the Progressive Party of Canada had more MPs than the Conservatives, but they turned down the chance of being official opposition and the position passed to the Tories.

In 1993 the Reform Party challenged whether the separatist Bloc Quebecois could hold the position of official opposition. The Speaker ruled in favour of the Bloc, however.

The leader of the Opposition party is called the "Leader of the Opposition" and is given an official residence in Ottawa.

Below is a list of leaders of Her Majesty's official opposition in Canada.

 
   
   
   
1. George Brown Liberal 1867-1872
2. Alexander Mackenzie Liberal 1873-1874
3. Sir John A. Macdonald Conservative 1874-1878
Alexander Mackenzie (2nd time) Liberal 1878-1880
4. Edward Blake Liberal 1880-1887
5. Sir Wilfrid Laurier Liberal 1887-1896
6. Sir Charles Tupper Conservative 1896-1901
7. Sir Robert Borden Conservative 1901-1911
Sir Wilfrid Laurier (2nd time) Liberal 1911-1919
* Daniel D. McKenzie (acting) Liberal 1919
8. W. L. Mackenzie King Liberal 1919-1921
9. Arthur Meighen Conservative 1921-1926
10. Hugh Guthrie Conservative 1926-1927
11. R. B. Bennett Conservative 1927-1930
W. L. Mackenzie King (2nd time) Liberal 1930-1935
R. B. Bennett (2nd time) Conservative 1935-1938
12. R. J. Manion Conservative 1938-1940
13. R. B. Hanson Conservative 1940-1943
* Gordon Graydon (acting) Conservative 1943-1945 Bracken not yet elected to Parliament
14. John Bracken [[Progressive Conservative Party of Canada|Progressive Conservative]] 1945-1948
15. George A. Drew Progressive Conservative 1948-1956
* William Earl Rowe (acting) Progressive Conservative 1954-1955, 1956 due to Drew's health
16. John G. Diefenbaker Progressive Conservative 1956-1957
17. Louis St. Laurent Liberal 1957-1958
18. Lester B. Pearson Liberal 1958-1963
John G. Diefenbaker (2nd time) Progressive Conservative 1963-1967
* Michael Starr (acting) Progressive Conservative 1967 Stanfield not yet elected to Parliament
19. Robert L. Stanfield Progressive Conservative 1967-1976
20. Joe Clark Progressive Conservative 1976-1979
21. Pierre E. Trudeau Liberal 1979-1980
Joe Clark (2nd time) Progressive Conservative 1980-1983
* Erik Nielsen (acting) Progressive Conservative 1983 Mulroney not yet elected to Parliament
22. Brian Mulroney Progressive Conservative 1983-1984
23. John N. Turner Liberal 1984-1990
* Herb Gray (acting) Liberal 1990 Chrétien not yet elected to Parliament
24. Jean Chrétien Liberal 1990-1993
25. Lucien Bouchard Bloc Québécois 1993-1996
* Gilles Duceppe (acting) Bloc Québécois 1996 BQ leadership contest
26. Michel Gauthier Bloc Québécois 1996-1997
27. Gilles Duceppe Bloc Québécois 1997
28. E. Preston Manning Reform 1997-2000
* Deborah Grey (acting) Canadian Alliance 2000 CA leadership contest
29. Stockwell Day Canadian Alliance 2000-2002
* John Reynolds (acting) Canadian Alliance 2002 CA leadership contest
30. Stephen Harper Canadian Alliance 2002-2004
* Grant Hill (acting) Conservative 2004 CPC leadership contest