List of Canadian Leaders of the Opposition

1 - George Brown was the unofficial leader of the Liberal Party in 1867 but failed to win a seat in the House of Commons in the September 20th election. Had Brown entered the Commons he would have almost certainly become Leader of the Opposition but as it was the Liberals remained largely leaderless until 1873, though Edward Blake was recognized as leader from 1869 - 1871, with leadership duties were held collectively by leading Liberal MPs, particularly Blake and Alexander Mackenzie.
2 - Tupper lost his seat in the 1900 Canadian election and resigned as party leader and Leader of the Opposition three months later.
3 - McKenzie served as interim Leader of the Opposition from Laurier's death until King's election as leader of the Liberal Party.
4 - Meighen failed to win his seat and immediately resigned as leader of the Conservative Party.
5 - Guthrie served as interim Leader of the Opposition from shortly after Meighen's resignation until Bennett's election as leader of the Conservative Party.
6 - Hanson served as interim Leader of the Opposition from Manion's resignation until Meighen's election as leader of the Conservative Party.
7 - Hanson continued as acting Leader of the Opposition throughout Meighen's term as Conservative leader, as Meighen failed in his attempts to win election to the House of Commons.
8 - Hanson continued as acting Leader of the Opposition from Bracken's election as PC leader until his own resignation.
9 - Graydon served as acting Leader of the Opposition from Hanson's resignation until Bracken entered Parliament in the 20th general election.
10 - Rowe served as acting Leader of the Opposition in winter 1954-55 due to Drew's poor health.
11 - Rowe again served as acting Leader of the Opposition due to Drew's poor health until Drew was replaced by Diefenbaker.
12 - Starr served as acting Leader of the Opposition from Stanfield's election as PC leader until Stanfield entered Parliament via byelection.
13 - Nielsen served as acting Leader of the Opposition for the two weeks preceding Clark's resignation from the post of leader of the PC Party.
14 - Nielsen continued as interim Leader of the Opposition during the 1983 Progressive Conservative leadership race in which Clark unsuccessfully ran to succeed himself.
15 - Nielsen continued as acting Leader of the Opposition from Mulroney's election as PC leader until Mulroney entered Parliament via byelection.
16 - Gray served as acting Leader of the Opposition from Chrétien's election as Liberal leader until Chrétien entered Parliament via byelection.
17 - Duceppe served as interim Leader of the Opposition during the 1996 Bloc Québécois leadership race initiated by Bouchard's sudden resignation from federal politics to become Premier of Quebec.
18 - Grey served as interim Leader of the Opposition during the 2000 Canadian Alliance leadership race in which Manning unsuccessfully ran to succeed himself.
19 - Grey continued as acting Leader of the Opposition from Day's election as Alliance leader until Day entered Parliament via byelection.
20 - Reynolds served as interim Leader of the Opposition during the 2002 Canadian Alliance leadership race in which Day unsuccessfully ran to succeed himself.
21 - Reynolds continued as acting Leader of the Opposition from Harper's election as Alliance leader until Harper entered Parliament via byelection.
22 - Hill served as interim Leader of the Opposition during the 2004 Conservative Party of Canada leadership race in which Harper successfully ran to succeed himself.
23 - Although the PC Party and Canadian Alliance were recognized as merged on December 7, 2003 by Elections Canada, they did not merge their Parliamentary caucuses until February 2, 2004.