The 1975 Ontario general election was held on September 18, 1975, to elect the 125 members of the 30th Legislative Assembly of Ontario (Members of Provincial Parliament, or "MPPs") of the Province of Ontario, Canada.

The Ontario Progressive Conservative Party, led by Bill Davis and campaigning under the slogan, "Your Future. Your choice.", won a tenth consecutive term in office but lost its majority in the legislature for the first time since the 1945 election. The PC party lost 27 seats from its result in the previous election.

The social democratic Ontario New Democratic Party, led by Stephen Lewis with the slogan "Tomorrow starts today", doubled its representation in the legislature, and became the Official Opposition on the strength of a campaign which called for rent control in Ontario and highlighted horror stories of individuals victimized by bad landlords who imposed exorbitant rent increases. The campaign forced Davis' Tories to promise to implement rent controls shortly before the election.

The Ontario Liberal Party, led by Robert Nixon, won 16 additional seats, but lost the role of Official Opposition to the NDP. One member of its caucus was elected as a Liberal-Labour candidate.

Expansion of Legislative Assembly An Act passed in May 1975 provided for an increase from 117 to 125 MPPs in the next Assembly:

Abolished ridings New ridingsDrawn from parts of other ridings Brockfrom part of Lincoln London Centrefrom parts of London North and London South Scarborough—Ellesmerefrom parts of Scarborough North, Scarborough West and Scarborough Centre Wilson Heightsfrom part of DownsviewReorganization of ridings Halton East Halton West Burlington South Halton—Burlington Oakville Glengarry Grenville—Dundas Stormont Carleton-Grenville Cornwall Stormont—Dundas—Glengarry Huron Middlesex North Middlesex South Huron—Middlesex Middlesex York-Forest Hill York South Oakwood Oriole York SouthDivision of ridings Peel North Brampton Mississauga North Waterloo South Cambridge Kitchener—Wilmot Peel South Mississauga East Mississauga SouthRenaming of ridings Brant Brant—Oxford—Norfolk Welland South Erie Essex—Kent Essex North Grey South Grey Hastings Hastings—Peterborough High Park High Park—Swansea Kent Kent—Elgin Thunder Bay Lake Nipigon Wellington—Dufferin Wellington—Dufferin—Peel Sandwich—Riverside Windsor—Riverside Windsor West Windsor—SandwichConsequential renaming of ridings on the creation of the Regional Municipality of Durham Durham Ontario Ontario South Durham East Durham North Durham West

Campaign

+ Riding contests, by number of candidates (1976) CandidatesPCLibLLNDPCommIndLtnSCTotal366 64 2 66 198441 41 41 19 5 9 6 2 164515 15 15 11 7 6 5 1 7562 2 2 2 3 1 1271 1 1 1 2 1 7Total125 123 2 125 33 17 15 13 3 456

Among the independent candidates, there were 12 from the Social Credit League of Ontario who were not officially recognized as such as the party did not qualify for official party status under the Election Finances Reform Act, 1975.

Opinion polls

+ Evolution of voting intentions at provincial level Polling firmLast day of survey Source PCO ONDP OLP Other SampleElection 1975September 18, 197536.0728.9434.040.95March 19753042Election 1971June 9, 197744.527.127.80.6

Results Summary

! colspan=2 rowspan=2 | Political party ! rowspan=2 | Party leader ! colspan=4 | MPPs ! colspan=4 | Votes |- ! Candidates !1971 !1975 !± !# ! ± !% ! ± (pp)

|style="text-align:left;"|Bill Davis | 125 || 78 || 51 || 27 || 1,192,592 || 272,721 || 36.07% || 8.43

|style="text-align:left;"|Stephen Lewis | 125 || 19 || 38 || 19 || 956,904 || 63,025 || 28.94% || 1.79

|rowspan="2" style="text-align:left;"|Robert Nixon | 123 || 20 || 35 || 15 || 1,125,615 || 211,873 || 34.04% || 6.29

| 2 || – || 1 || 1 || 9,066 || 9,066 || 0.27% ||Returned

|style="text-align:left;"|William Stewart | 33 || – || – || – || 9,120 || 7,500 || 0.28% || 0.23

|style="text-align:left;"|Terry Coughlin | 15 || – || – || – || 4,437 || 4,437 || 0.13% ||New

|style="text-align:left;"|Alcide Hamelin|| 13 || – || – || – || 4,146 || 2,942 || 0.13% || 0.09

| || 17 || – || – || – || 4,093 || 12,866 || 0.12% || 0.40

| || 3 || – || – || – || 424 || 424 || 0.01% ||New |- ! colspan="3" style="text-align:left;" | Total |456||117 ! " colspan="2"|125 ! " colspan="2"|3,306,397 ! " colspan="2"| 100.00% |- | colspan="7" style="text-align:left;" | Rejected ballots | 17,937 | 122 | colspan="2"| |- | colspan="7" style="text-align:left;" | Voter turnout | 3,310,776 | 13,558 | 67.82 | 5.71 |- | colspan="7" style="text-align:left;" | Registered electors | 4,503,142 | 398,635 | colspan="2"|

Vote and seat summaries

+ Seats and popular vote by party Party Seats Votes Change (pp) /Liberal-Labour

Synopsis of results