For the Leader of the Opposition in other parliamentary systems, see Leader of the Opposition.
The Leader of the Opposition in Ontario is usually leader of the largest party in the Ontario legislature which is not the government. The current official opposition is formed by the Ontario Progressive Conservative Party; Patrick Brown is the current Leader of the Opposition.
Ontario’s first Leader of the Opposition was Edward Blake of the Ontario Liberal Party who held the position from 1869 until 1871 when he became Premier of Ontario (Archibald McKellar had previously led the Liberal Party in the legislature for two years, but was not formally recognized as opposition leader).

Archibald McKellar (Liberal) 1867-1869 was not formally recognized as opposition leader, but led the Liberal Party in the legislature.

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Leader
Party
Took office
Left office

    1.
Edward Blake
Liberal
December 1869
December 1871

    2.
Matthew Crooks Cameron
Conservative
December 1871
1878

    3.
William Ralph Meredith
October 1878
October 1894

    4.
George Marter
October 1894
April 1896

    5.
James Whitney
April 1896
January 1905

    6.
George William Ross
Liberal
February 1905
January 1907

    7.
George Graham
January 1907
August 1907

    8.
Alexander Grant MacKay
August 1907
1911

    9.
Newton Wesley Rowell
December 1911
1917

    10.
William Proudfoot
February 1918
October 1919

    11.
Hartley Dewart
1919
October 1921

    12.
Wellington Hay
March 1922
June 1923

    13.
William Sinclair 1 2
August 1923
June 1934

    14.
George Henry
Conservative
July 1935
December 1938

    15.
George Drew
Conservative/Progressive Conservative
1939
1943

    16.
Ted Jolliffe
CCF
August 1943
June 1945

    17.
Farquhar Oliver
Liberal
July 1945
June 1948

     –
Ted Jolliffe (second time)
CCF
July 1948
November 1951

     –
Farquhar Oliver 3 (second time)
Liberal
1951
April 1958

    18.
John Wintermeyer
April 1958
August 1963

     –
Farquhar Oliver 4 (third time)
October 1963
September 1964

    19.
Andy Thompson
September 196
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