This is a list of results of leadership elections for the Ontario Liberal Party, a political party in Ontario, Canada.

Note: Before 1919, the leaders of the Ontario Liberal Party were chosen by its elected Members of the Legislative Assembly. There were calls for a more open process as early as 1907.

1919 leadership convention

(Held on June 26, 1919 at the Foresters' Hall, 22 College Street, Toronto.)^[1]

First ballot:

• Hartley Dewart 147
• J.C. Tolmie 97
• J.C. Elliott 37
• William Proudfoot 23
• Thomas McMillan 8

Second ballot:

• Hartley Dewart 158
• J.C. Tolmie 121
• J.C. Elliott 24

Charles Martin Bowman, MPP for Bruce North; W.T.R. Preston, editor of the Port Hope Evening Guide, Rev. W. G. Charlton of Aylmer, and A. J. Young of Toronto were nominated but declined. Frederick Forsyth Pardee, Member of Parliament for Lambton West was to be nominated but sent a message to the convention declining.^[2]

1922 leadership convention

(Held on March 3, 1922 at the Foresters' Hall, 22 College Street, Toronto.)^[3]

• Wellington Hay won with clear majority on the first ballot
• J.C. Tolmie
• W.E.N. Sinclair

(Note: The vote totals do not appear to have been announced.)

1930 leadership convention

(Held on December 16–17, 1930 at the King Edward Hotel in Toronto.)^[4]

• Mitchell Hepburn 427
• Elmore Philpott 97

W.E.N. Sinclair and Sydney Tweed both withdrew from the race before balloting.

1943 leadership convention

(Held on April 30, 1943 at the King Edward Hotel in Toronto.)

• Harry Nixon 418
• Arthur Roebuck 85
• Thomas McQuesten 40
• Walter Thomson 22

There were 8 spoiled ballots. Premier Gordon Conant had also been a candidate but collapsed the morning of the leadership vote and withdrew.

1945 leadership election

(Held on April 2, 1945 at the King Edward Hotel in Toronto.)

• Mitchell Hepburn acclaimed

Harry Nixon resigned as Liberal leader on December 10, 1944 and nominated Hepburn to succeed him as parliamentary leader until a leadership convention could be held.^[5] Following the defeat of George Drew's Conservative government in a non-confidence motion, Hepburn was elected Acting Leader on April 2, 1945, at a joint meeting held at the King Edward Hotel of Ontario Liberal MPPs, federal Ontario Liberal MPs the party executive and other party officials in order to lead the party into the election. The move was to be affirmed by a party convention to be held on May 1, but this was cancelled due to the 1945 provincial election being underway.^[6][7][8] Hepburn was defeated in the 1945 provincial election, and Farquhar Oliver was chosen as the Ontario Liberal Party's parliamentary leader on July 4, 1945.

1947 leadership convention

(Held on May 16, 1947 at the King Edward Hotel in Toronto)^[9][10]

• Farquhar Oliver elected
• Colin Campbell
• Allan A. Lamport
• Alvin P. Cadeau
• W.A. Gunn
• P.M. Dewan and W.A. Moore both withdrew from the race before balloting.

(Note: Complete vote totals were not reported. Oliver received 492 of 661 votes cast)^[10]

1950 leadership convention

(Held on November 10, 1950 at the Royal York Hotel in Toronto.)^[11]

First ballot:

• Walter Thomson 296
• Harry Cassidy 156
• John G. Brown 149
• Campbell Calder 69
• Henry Arnott Hicks 28
• Charles Winnans Cox 24
• Norman Hipel 12
• J.J. Sullivan 4

Second ballot (Sullivan eliminated; Hicks, Cox and Hipel withdrew):

• Walter Thomson 334
• Harry Cassidy 194
• John G. Brown 166
• Campbell Calder 50

Third ballot (Calder eliminated):

• Walter Thomson 365
• Harry Cassidy 220
• John G. Brown 116

1954 leadership convention

(Held on April 9, 1954 at the Royal York Hotel in Toronto.)^[12]

• Farquhar Oliver 412
• Albert Wren 162
• Bob Temple 46

1958 leadership convention

(Held on April 20, 1958 at the King Edward Hotel in Toronto.)^[13]

First ballot:

• Walter Harris 304
• John Wintermeyer 264
• Joe Greene 88
• Vernon Singer 43
• Ross Whicher 39
• Arthur Reaume 32
• Albert Wren 7

Wren eliminated and endorsed Wintermeyer; Whicher and Reaume withdrew and endorsed Wintermeyer.^[14]

Second ballot:

• John Wintermeyer 369
• Walter Harris 354
• Joe Greene45
• Vernon Singer 21

Singer eliminated.

Third ballot:

• John Wintermeyer 398
• Walter Harris 349
• Joe Greene 14

1964 leadership convention

(Held on September 19–20, 1964 at the Royal York Hotel in Toronto.)

1967 leadership convention

(Held on January 6, 1967 at the Royal York Hotel, Toronto)^[15]

• Robert Nixon acclaimed

(Nixon was elected interim leader by the caucus on November 16, 1966 following the resignation of Andrew Thompson. Nixon had suggested that Charles Templeton may become permanent leader but members of his caucus spoke in opposition and Templeton decline to run. Nixon was acclaimed as permanent leader at the party's 1967 convention. He announced his resignation as party leader in 1972, but subsequently entered the race to succeed himself in 1973.)

1973 leadership convention

(Held on October 28, 1973 at the Royal York Hotel in Toronto.)

1976 leadership convention

(Held on January 24–25, 1976 at the Four Seasons Sheraton Hotel, Toronto)

1982 leadership convention

(Held on February 21, 1982 at the Sheraton Centre Toronto Hotel, Toronto).

  = Eliminated from next round

  = Withdrew nomination

  = Winner

1992 leadership convention

(Held February 8–9, 1992 at the Copps Coliseum in Hamilton.)

  = Eliminated from next round

  = Withdrew nomination

  = Winner

^A There were 21 spoiled ballots on the final count.

1996 leadership convention

(Held November 30 – December 1, 1996 at the Maple Leaf Gardens, Toronto)

  = Eliminated from next round

  = Withdrew nomination

  = Winner

^A Castrilli initially withdrew from the 2nd ballot but subsequently returned, causing a delay in voting

2013 leadership election

(Held January 26, 2013 at the Maple Leaf Gardens, Toronto)

  = Eliminated from next round

  = Withdrew nomination

  = Winner

Delegate support by ballot

Candidate		Committed[16]	Ballot 1	Ballot 2		Ballot 3
Name		Votes	Votes	Votes	+/- (pp)	Votes	+/- (pp)
	Sandra Pupatello	509 27.4%	599 28.7%	817 39.4%	+10.7	866 43.0%	+5.8%
	Kathleen Wynne	468 25.2%	597 28.6%	750 36.2%	+7.6	1,150 57.0%	+20.8
	Gerard Kennedy	260 14.0%	281 13.5%	285 13.7%	+0.2	Endorsed Wynne
	Harinder Takhar	244 13.1%	235 11.3%	18 0.9%	-10.4	Endorsed Pupatello[A]
	Charles Sousa	204 11.0%	222 10.7%	203 9.8%	-0.9	Endorsed Wynne
	Eric Hoskins	105 5.7%	150 7.2%	Endorsed Wynne
Independent		67 3.6%
	Glen Murray	Endorsed Wynne
Votes cast and net change by ballot
Total		1,857	2,084	2,073	-11	2,016	-57

^A Takhar endorsed Pupatello before the second ballot voting took place, but after the deadline to drop off the ballot.

2020 leadership election

(Held March 6–7, 2020 at the International Centre, Mississauga)

There was one spoiled ballot.^[18]

2023 leadership election

(Results announced December 2, 2023 at the Metro Toronto Convention Centre)

A leadership election was held December 2, 2023 due to the June 2, 2022 resignation of Steven Del Duca as party leader following his party's poor result in the 2022 Ontario general election.

  = Winner

Results by round

Candidate		1st round				2nd round				3rd round
		Votes cast	%	Points allocated	%	Votes cast	%	Points allocated	%	Votes cast	%	Points allocated	%
	Bonnie Crombie			5,559	42.96%			6,047	46.73%			6,911	53.40%
	Nathaniel Erskine-Smith			3,320	25.66%			3,792	29.30%			6,029	46.59%
	Yasir Naqvi			2,760	21.33%			3,101	23.96%	Eliminated
	Ted Hsu			1,300	10.05%	Eliminated
Total			100%	12,939	100%		100%	12,940	100%		100%	12,940	100%

According to the party, 22,827 party members cast ballots^[19] out of a total membership of over 100,000.^[20]