She leads the New Democratic Party (NDP), which has held the second largest number of seats in the Legislative Assembly since the 2018 provincial election.

1 The Liberals were recognized as the Official Opposition following the 1923 election by the governing Conservatives, despite the fact that the United Farmers of Ontario had more seats.

9 John Tory was chosen as leader of the Ontario Progressive Conservative Party on September 18, 2004, but did not hold a seat in the legislature.

On September 28 the party announced that Bob Runciman would act as interim PC leader until Tory entered the legislature.

[5] 12 Vic Fedeli was chosen interim leader of the PC Party by caucus on January 26, 2018, one day after Patrick Brown resigned due to allegations of sexual misconduct.

13 Peter Tabuns was chosen as interim leader by the NDP caucus on June 28, 2022, following the resignation of Andrea Horwath.