Leaders of Her Majesty's Loyal Opposition (Canada)
The Leader of the Official Opposition is the leader of the party with the second-most seats in the House of Commons.
| Opposition Leader | Opposing Prime Minister | Term | Party |
| Alexander MacKenzie | MacDonald | 1867-1873 | Liberal |
| John A. MacDonald | MacKenzie |
1873-1978 | Conservative |
| Alexander MacKenzie (2nd time) | MacDonald | 1878-1880 | Liberal |
| Edward Blake | MacDonald |
1880-1887 | Liberal |
| Wilfred Laurier | MacDonald, Abbott, Thompson, Bowell, Tupper | 1887-1896 | Liberal |
| Charles Tupper | Laurier |
1896-1900 | Conservative |
| Robert Bordern | Laurier |
1900-1911 | Unionist |
| Wilfred Laurier (2nd time) | Borden | 1911-1920 | Liberal |
| W.L. Mackenzie King | Borden, Meighen | 1920-1921 | Liberal |
| Arthur Meighen | Mackenzie King |
1921-1926 | Progressive Conservative |
| W.L. Mackenzie King (2nd time) | Meighen | 1926 | Liberal |
| Hugh Guthie | Mackenzie King |
1926-1927 | Progressive Conservative |
| Richard Bennett | Mackenzie King | 1927-1930 | Progressive Conservative |
| W.L. Mackenzie King (3rd time) | Bennett | 1930-1935 | Liberal |
| Richard Bennett (2nd time) | Mackenzie King | 1935-1938 | Progressive Conservative |
| R.J. Manion | Mackenzie King |
1938-1940 | Progressive Conservative |
| R.B. Hanson | Mackenzie King |
1940-1943 | Progressive Conservative |
| John Bracken | Mackenzie King |
1943-1948 | Progressive Conservative |
| George Drew | Mackenzie King, St. Laurent |
1948-1956 | Progressive Conservative |
| John Diefenbaker | St. Laurent | 1956-1957 | Progressive Conservative |
| Louis St. Laurent | Diefenbaker |
1957-1958 | Liberal |
| Lester B. Pearson | Diefenbaker |
1958-1963 | Liberal |
| John Diefenbaker (2nd time) | Pearson | 1963-1967 | Progressive Conservative |
| Robert Stanfield | Pearson, Trudeau |
1967-1976 | Progressive Conservative |
| Joe Clark | Trudeau | 1976-1979 | Progressive Conservative |
| Pierre Trudeau | Clark |
1979-1980 | Liberal |
| Joe Clark (2nd time) | Trudeau | 1980-1983 | Progressive Conservative |
| Brian Mulroney | Trudeau, Turner |
1983-1984 | Progressive Conservative |
| John Turner | Mulroney |
1984-1989 | Liberal |
| Herbert Gray (acting) | Mulroney |
1989-1990 | Liberal |
| Jean Chrétien | Mulroney, Campbell |
1990-1993 | Liberal |
| Lucien Bouchard | Chrétien |
1993-1996 | Bloc Quebecois |
| Gilles Duceppe (acting) | Chrétien | 1996 | Bloc Quebecois |
| Michel Gauthier | Chrétien |
1996-1997 | Bloc Quebecois |
| Gilles Duceppe (2nd time) | Chrétien | 1997 | Bloc Quebecois |
| Preston Manning | Chrétien |
1997-2000 |
Reform |
| Deborah Grey (acting) | Chrétien |
2000 |
Reform |
| Stockwell Day | Chrétien |
2000-2001 |
Canadian Alliance |
| John Reynolds (acting) | Chrétien | 2001-2002 | Canadian Alliance |
| Stephen Harper | Chrétien, Martin |
2002- 2004 |
Canadian Alliance |
| Grant Hill (acting) | Martin | 2004 | Conservative |
| Stephen Harper (2nd time) | Martin | 2004 - 2006 | Conservative |
| Bill Graham (acting) | Harper |
2006 | Liberal |
| Stephane Dion | Harper |
2006 - 2008 | Liberal |
| Michael Ignatieff | Harper |
2006 - 2011 | Liberal |
| Jack Layton | Harper |
2011 - | New Democratic Party |
"Acting" opposition leaders most commonly hold office during a party leadership campaign, or in other interim situtations when a new party leader is being selected.