The Leader of Her Majesty's Loyal Opposition (French: chef de la loyale opposition de Sa Majesté), or simply the Leader of the Opposition (French: chef de l'opposition) is the leader of Canada's Official Opposition, the party possessing the most seats in the House of Commons but is not the governing party or part of the governing coalition. The current Leader of the Opposition is interim leader of the Conservative Party, Rona Ambrose.

Though the Leader of the Opposition must be a member of the House of Commons, the office should not be confused with the Leader of the Opposition in the House of Commons, which is the formal title of the opposition house leader. There is also a Leader of the Opposition in the Senate, who is usually of the same party as the Leader of the Opposition in the house.

The Leader of the Opposition is entitled to the same levels of pay and protection as a Cabinet minister. He or she is entitled to reside at the official residence of Stornoway and ranks fourteenth on the Order of Precedence, after Cabinet ministers and before lieutenant governors of the provinces. In the House of Commons seating plan, the Leader of the Opposition sits directly across from the Prime Minister.

Liberal Leader of the Official Opposition

• Alexander Mackenzie (1st of two) (March 1873 to November 5, 1873)

Liberal-Conservative Leader of the Official Opposition

• Sir John A. Macdonald (November 6, 1873 to October 16, 1878)

Liberal Leaders of the Official Opposition

• Alexander Mackenzie (2nd of two) (October 17, 1878 to April 27, 1880)
  • vacant (April 28, 1880 to May 3, 1880)
• Edward Blake (May 4, 1880 to June 2, 1887)
  • vacant (June 3, 1887 to June 22, 1887)
• Sir Wilfrid Laurier (1st of two) (June 23, 1887 to July 10, 1896)

Conservative Leaders of the Official Opposition

• Sir Charles Tupper (July 11, 1896 to February 5, 1901)
• Sir Robert Borden (February 6, 1901 to October 9, 1911)

Liberal Leaders of the Official Opposition

• Sir Wilfrid Laurier (2nd of two) (October 10, 1911 to February 17, 1919)
  • Daniel Duncan McKenzie (acting) (February 17, 1919 to August 7, 1919)
• William Lyon Mackenzie King (1st of three) (August 7, 1919 to December 28, 1921)

Conservative Leader of the Official Opposition

• Arthur Meighen (December 9, 1921 to June 28, 1926)

Liberal Leader of the Official Opposition

• William Lyon Mackenzie King (2nd of three) (June 29, 1926 to September 24, 1926)

Conservative Leaders of the Official Opposition

• Arthur Meighen (Resigned on September 24, 1926)
  • vacant (September 25, 1926 to October 10, 1926)
• Hugh Guthrie (acting) (October 11, 1926 to October 11, 1927)
• Richard B. Bennett (1st of two) (October 12, 1927 to August 6, 1930)

Liberal Leader of the Official Opposition

• William Lyon Mackenzie King (3rd of three) (August 7, 1930 to October 22, 1935)

Conservative Leaders of the Official Opposition

• Richard B. Bennett (2nd of two) (October 23, 1935 to July 6, 1938)
• Robert Manion (July 7, 1938 to May 13, 1940)
  • Richard Hanson (acting) (May 14, 1940 to 1943)

Progressive Conservative Leaders of the Official Opposition

• Progressive was added to the Party name in 1943
  • Gordon Graydon (acting) (1943 to June 10, 1945)
• John Bracken (June 11, 1945 to July 20, 1948)
  • vacant (July 21, 1948 to October 1, 1948)
• George A. Drew (1st of two) (October 2, 1948 to November 1, 1954)
  • William Earl Row (acting, 1st of two) (November 1, 1954 to February 1, 1955)
• George A. Drew (2nd of two) (February 1, 1955 to August 1, 1956)
  • William Earl Row (acting, 2nd of two) (August 1, 1956 to December 13, 1956)
• John G. Diefenbaker (1st of two) (December 14, 1956 to June 20, 1957)

Liberal Leaders of the Official Opposition

• Louis St. Laurent (June 21, 1957 to January 15, 1958)
• Lester B. Pearson (January 16, 1958 to April 21, 1963)

Progressive Conservative Leaders of the Official Opposition

• John G. Diefenbaker (2nd of two) (April 22, 1963 to September 8, 1967)
  • Michael Starr (acting) (September 8, 1967 to November 5, 1967)
• Robert Stanfield (November 6, 1967 to February 21, 1976)
• Joe Clark (1st of two) (February 22, 1976 to June 3, 1979)

Liberal Leader of the Official Opposition

• Pierre Elliott Trudeau (June 4, 1979 to March 2, 1980)

Progressive Conservative Leaders of the Official Opposition

• Joe Clark (2nd of two) (March 3, 1980 to February 1, 1983)
  • Erik Nielsen (acting) (February 2, 1983 to August 28, 1983)
• Brian Mulroney (August 29, 1983 to September 16, 1984)

Liberal Leaders of the Official Opposition

• John Turner (September 17, 1984 to February 9, 1990)
  • Herb Gray (acting) (February 8, 1990 to December 20, 1990)
• Jean Chrétien (December 21, 1990 to October 24, 1993)

Bloc Québécois Leaders of the Official Opposition

• Lucien Bouchard (October 25, 1993 to January 14, 1996)
  • Gilles Duceppe (acting) (January 15, 1996 to February 16, 1996)
• Michel Gauthier (February 17, 1996 to March 14, 1997)
• Gilles Duceppe (March 15, 1997 to June 1, 1997)

Reform Leader of the Official Opposition

• Preston Manning (June 2, 1997 to March 26, 2000)

Canadian Alliance Leaders of the Official Opposition

• The Reform Party of Canada changed its name to the Canadian Alliance
  • Deborah Grey (acting) (March 27, 2000 to September 10, 2000)
• Stockwell Day (September 11, 2000 to December 11, 2001)
  • John Reynolds (acting) (December 12, 2001 to May 20, 2002)
• Stephen Harper (1st of two) (May 21, 2002 to January 8, 2004)
  • Grant Hill (acting) (January 9, 2004 to February 1, 2004)

Conservative Leaders of the Official Opposition

• Party was created from the merger of the Progressive Conservative Party of Canada and the Canadian Alliance on December 7, 2013. Parliamentary merger occurred on February 2, 2004
  • Grant Hill (acting) (February 2, 2004 to March 19, 2004)
• Stephen Harper (2nd of two) (March 20, 2004 to February 5, 2006)

Liberal Leaders of the Official Opposition

• Liberal leader Paul Martin resigns as leader after stepping down as Prime Minister in the morning of February 6, 2006
  • Bill Graham (acting) (February 6, 2006 to December 1, 2006)
• Stéphane Dion (December 2, 2006 to December 9, 2008)
• Michael Ignatieff (December 10, 2008 to May 1, 2009 as acting) (May 2, 2009 to May 1, 2011)

New Democratic Leaders of the Official Opposition

• Jack Layton (May 2, 2011 to August 22, 2011)
  • Nycole Turmel (acting) (August 23, 2011 to March 23, 2012)
• Thomas Mulcair (March 24, 2012 to November 4, 2015)

Conservative Leader of the Official Opposition

• Conservative Party of Canada Leader Stephen Harper stepped down as leader of the party after losing the October 19, 2015 Federal Election. His resignation was effective November 5, 2015
  • Rona Ambrose (acting) (November 5, 2015 to present)