Nepean is a provincial electoral district that has existed from 1987 to 1999, and again since 2018. The riding was re-created federally with the 2012 redistribution process. That same process was followed by the Ontario government, meaning the provincial ridings follow a similar boundary division for the 2018 provincial election.

Nepean was created in 1987 out of part of Carleton. It was represented by a Liberal MPP for eight years before it was won by then 25-year-old Progressive Conservative John Baird. Baird represented Nepean for four years. In 1999, the provincial redistribution resulted in Nepean being abolished as it was split between the new Ottawa West—Nepean and Nepean—Carleton ridings.

Provincial law has required that southern Ontario's electoral boundaries have the same boundaries provincially and federally. The federal boundaries were redistributed in 2012 in time for the 2015 federal election, meaning Ontario's first provincial election under the new boundaries was the 2018 election.

Nepean
Assembly	Years	Member		Party
34th	1987–1990		Hans Daigeler	Liberal
35th	1990–1995
36th	1995–1999		John Baird	Progressive Conservative
Riding dissolved into Nepean—Carleton and Ottawa West—Nepean
Riding re-created from Nepean—Carleton
42nd	2018–2022		Lisa MacLeod	Progressive Conservative
43rd	2022–present

v t e 2022 Ontario general election
Party	Candidate	Votes	%	±%	Expenditures
	Progressive Conservative	Lisa MacLeod	17,123	39.26	−5.87	$56,906
	Liberal	Tyler Watt	15,029	34.46	+14.85	$68,470
	New Democratic	Brian Double	8,435	19.34	−9.19	$5,327
	Green	Kaitlyn Tremblay	1,696	3.89	−1.28	$381
	New Blue	Kathleen Corriveau	964	2.21		$4,503
	Ontario Party	Bryan Emmerson	370	0.85		$0
Total valid votes/Expense limit			43,617	99.43	+0.33	$134,511
Total rejected, unmarked, and declined ballots			249	0.57	-0.33
Turnout			43,866	45.89	-12.84
Eligible voters			96,076
	Progressive Conservative hold		Swing		−10.36
Source(s) "Summary of Valid Votes Cast for Each Candidate" (PDF). Elections Ontario. 2022. Archived from the original on 2023-05-18. "Statistical Summary by Electoral District" (PDF). Elections Ontario. 2022. Archived from the original on 2023-05-21.

v t e 2018 Ontario general election
Party	Candidate	Votes	%	±%
	Progressive Conservative	Lisa MacLeod	23,899	45.13	+1.90
	New Democratic	Zaff Ansari	15,110	28.53	+15.04
	Liberal	Lovina Srivastava	10,383	19.61	-16.69
	Green	James O'Grady	2,739	5.17	-0.34
	Libertarian	Mark A. Snow	415	0.78
	None of the Above	Raphael Louis	351	0.66
	Objective Truth	Derrick Lionel Matthews	60	0.11
Total valid votes			52,957	100.0
Turnout				60.3
Eligible voters			90,987
	Progressive Conservative pickup new district.
Source: Elections Ontario

v t e 1995 Ontario general election: Nepean
Party	Candidate	Votes	%	Expenditures
	Progressive Conservative	John Baird	17,510	49.66	$40,800.37
	Liberal	Hans Daigeler	13,575	38.50	$45,021.83
	New Democratic	John Sullivan	3,274	9.29	$15,380.57
	Green	Frank de Jong	390	1.11	$0.00
	Natural Law	Brian E. Jackson	259	0.73	$0.00
	Freedom	Cathy Frampton	252	0.71	$2,307.70
Total valid votes			35,260	100.00
Rejected, unmarked and declined ballots			363
Turnout			35,623	64.97
Electors on the lists			54,832

1990 provincial election: Nepean
Party		Candidate	Votes
	Liberal	(x)Hans Daigeler	13,723
	Progressive Conservative	Doug Collins	9,870
	New Democratic Party	John Raudoy	7,453
	Green	Dan Roy	933
	Libertarian	Dan Weiler	349

1987 provincial election: Nepean
Party		Candidate	Votes
	Liberal	Hans Daigeler	13,951
	Progressive Conservative	(x)Bob Mitchell	10,315
	New Democratic Party	Larry Jones	4,526

• Map of riding for 2018 election

45°16′30″N 75°45′29″W / 45.275°N 75.758°W / 45.275; -75.758