Stormont—Dundas—South Glengarry (formerly Stormont—Dundas and Stormont—Dundas—Charlottenburgh) is a federal electoral district in Ontario, Canada, that has been represented in the House of Commons of Canada since 1968.

The district includes the United Counties of Stormont, Dundas and Glengarry, excluding the Township of North Glengarry.

The electoral district was created in 2003, from the Stormont—Dundas—Charlottenburgh and Glengarry—Prescott—Russell districts. In turn, the Stormont-Dundas-Charlottenburgh district was formed from the Stormont-Dundas district.

Stormont—Dundas was a federal electoral district from 1968 to 1999. The riding was created in 1966 from parts of Stormont and Grenville—Dundas ridings.

It initially consisted of the County of Stormont including the City of Cornwall, and the townships of Williamsburg and Winchester (in the County of Dundas). In 1976, it was redefined to consist of all of the counties of Dundas and Stormont, and the Township of Charlottenburgh in Glengarry County, but excluding the Village of Lancaster. In 1987, it was redefined to consist of the counties of Dundas and Stormont, excluding Akwesasne Indian Reserve No. 59. In 1996, it was redefined to include the Township of Charlottenburgh and Akwesasne Indian Reserve No. 59.

The electoral district's name was changed in 1999 to Stormont—Dundas—Charlottenburgh. It was represented in the House of Commons of Canada from 1997 to 2004, and in the Legislative Assembly of Ontario from 1999 to 2007. It consisted of parts of the United Counties of Stormont, Dundas and Glengarry: the Township of Charlottenburgh (Glengarry County), the counties of Dundas and Stormont, and Akwesasne Indian Reserve No. 59.

Stormont—Dundas—South Glengarry was created in 2003: 91.5% of it came from Stormont—Dundas—Charlottenburgh, and 4.9% from Glengarry—Prescott—Russell ridings.

This riding was unchanged during the 2012 electoral redistribution.

Following the 2022 Canadian federal electoral redistribution, this riding will be renamed Stormont—Dundas—Glengarry at the first election held after approximately April 2024. It will gain North Glengarry from Glengarry—Prescott—Russell in the process.

According to the 2021 Canadian census

Ethnic groups: 86.9% White, 7.3% Indigenous, 2.5% South Asian, 1.1% Black

Languages: 77.5% English, 20.0% French

Religions: 68.3% Christian (44.4% Catholic, 6.6% United Church, 3.8% Anglican, 2.8% Presbyterian, 10.7% Other), 1.9% Muslim, 28.0% none

Median income: $39,200 (2020)

Average income: $47,160 (2020)

This riding has elected the following members of Parliament:

Parliament	Years	Member		Party
Stormont—Dundas Riding created from Grenville—Dundas and Stormont
28th	1968–1972		Lucien Lamoureux	Independent
29th	1972–1974
30th	1974–1979		Ed Lumley	Liberal
31st	1979–1980
32nd	1980–1984
33rd	1984–1988		Norman Warner	Progressive Conservative
34th	1988–1993		Bob Kilger	Liberal
35th	1993–1997
36th	1997–2000
Stormont—Dundas—Charlottenburgh
37th	2000–2004		Bob Kilger	Liberal
Stormont—Dundas—South Glengarry
38th	2004–2006		Guy Lauzon	Conservative
39th	2006–2008
40th	2008–2011
41st	2011–2015
42nd	2015–2019
43rd	2019–2021		Eric Duncan
44th	2021–present