In Canada, the Leader of the Official Opposition in the Senate (French: Chef de l'opposition au Sénat) is the leader of the largest party in the Senate not in government.

Even though the position's name is very similar to the Leader of the Opposition in the House of Commons (the Opposition House Leader), the Leader of the Opposition in the Senate's role is more analogous to the Leader of the Official Opposition because its holder is the leader of the party's Senate caucus. The responsibilities that, in the House of Commons, are done by the house leaders—including day-to-day scheduling of business—are undertaken in the Senate by Government and Opposition deputy leaders and Opposition whips.

Leaders of the Opposition in the Senate of Canada

Liberal Leader of the Opposition

• Luc Letellier de St-Just (July 1, 1867 to November 5, 1873)

Conservative Leader of the Opposition

• Alexander Campbell (November 7, 1873 to October 8, 1878)

Liberal Leader of the Opposition

• Sir Richard William Scott (October 8, 1878 to April 27, 1896)

Conservative Leaders of the Opposition

• Sir Mackenzie Bowell (April 27, 1896 to March 1, 1906)
• Sir James Alexander Lougheed (April 1, 1906 to October 6, 1911)

Liberal Leaders of the Opposition

• Sir Richard John Cartwright (October 6 1911 to September 24, 1912)
• Sir George William Ross (September 24, 1912 to March 7, 1914)
• Hewitt Bostock (March 19, 1914 to January 1, 1919)
• Raoul Dandurand (January 1, 1919 to December 31, 1919)
• Hewitt Bostock (2nd time) (January 1, 1920 to December 28, 1921)

Conservative Leaders of the Opposition

• Sir James Alexander Lougheed (2nd time) (December 28, 1921 to November 2, 1925)
• William Benjamin Ross (January 1, 1926 to June 28, 1926)

Liberal Leader of the Opposition

• Raoul Dandurand (2nd time) (June 29, 1926 to December 31, 1926)

Conservative Leaders of the Opposition

• William Benjamin Ross (2nd time) (December 31, 1926 to January 10, 1929)
• Wellington Bartley Willoughby (January 11, 1929 to August 7, 1930)

Liberal Leader of the Opposition

• Raoul Dandurand (3rd time) (August 7, 1930 to October 22, 1935)

Conservative Leaders of the Opposition

• Arthur Meighen (October 22, 1935 to January 26, 1942)
• Charles Colquhoun Ballantyne (January 26, 1942 to December 10, 1942)

Progressive Conservative Leaders of the Opposition

• Charles Colquhoun Ballantyne (December 11, 1942 to September 11, 1945)
• John Thomas Haig (September 12, 1945 to June 20, 1957)

Liberal Leader of the Opposition

• William Ross Macdonald (June 20, 1957 to April 21, 1963)

Progressive Conservative Leaders of the Opposition

• Alfred Johnson Brooks (April 22, 1963 to October 31, 1967)
• Jacques Flynn (October 31, 1967 to June 3, 1979)

Liberal Leader of the Opposition

• Raymond Joseph Perrault (June 3, 1979 to March 2, 1980)

Progressive Conservative Leader of the Opposition

• Jacques Flynn (2nd time) (March 3, 1980 to September 16, 1984)

Liberal Leaders of the Opposition

• Allan MacEachen (September 16, 1984 to November 30, 1991)
• Royce Herbert Frith (November 31, 1991 to October 25, 1993)

Progressive Conservative Leader of the Opposition

• John Lynch-Staunton (October 25, 1993 to February 1, 2004)

Conservative Leader of the Opposition

• John Lynch-Staunton (February 2, 2004 to September 30, 2004)
• Noël A. Kinsella (October 1, 2004 to February 7, 2006)

Liberal Leaders of the Opposition

• Dan Hays (February 8, 2006 to January 18, 2007)
• Céline Hervieux-Payette (January 18, 2007 to November 3, 2008)
• Jim Cowan (November 3, 2008 to January 29, 2014)

Liberal Senate caucus Leader of the Opposition

• Jim Cowan (January 29, 2014 to November 5, 2015)

Conservative Leader of the Opposition

• Claude Carignan (November 5, 2015 to Present)