Ristigouche-Sud-Est (or Ristigouche-Partie-Sud-Est until February 2024) is a municipality in Quebec, Canada, near the head of the Baie de Chaleur. It is a rural municipality without population centres, situated along the CN Railway line which hosts the VIA Rail Ocean (train) route; the nearest VIA station is Matapedia.

At the beginning of the 19th century, the voyage between Quebec and Saint John passed the Temiscouata Portage and via the Saint John River valley. After the War of 1812, it was decided to develop a new maritime route which was to be located away from the border. The Matapedia River valley was selected, and the route would be named Kempt Road, for General Sir James Kempt, then Governor-General of British North America. Construction started in 1830, under the supervision of William MacDonald, Frederic Fournier and Major Wolfe, but the route remained difficult and government decided to abandon it in 1857. A new path between Causapscal and the Restigouche was adopted in 1862, and in 1868 the Intercolonial Railway project that was to transform the British North American Colonies into Canada selected the Matapedia River road to be its route. On 1 July 1876, the Sainte-Flavie-Campbellton section was opened.

The township municipality was formed in 1907 when it separated from the Township Municipality of Ristigouche (now Saint-André-de-Restigouche).

On 17 April 1983, the 480 ha (4.8 km) Ristigouche Ecological Reserve was formed by the Quebec government.

In March 2013, the municipality was served notice of pursuit by the resource extractor Gastem for $1.5 million because the municipality sought to protect its drinking water source from fracking, by imposing an exclusion zone of 2 km around water wells. Gastem later ceded its exploration permits to Pétrolia [fr]. now a subsidiary of the French multinational oil producer Maurel et Prom [fr], The municipality had amassed $146,000 in its charitable legal defence fund as of March 2015. Gastem offered an amicable resolution at that time for that cost. Ultimately, a judge of the Superior Court of Quebec ruled in the township's favour in 2017.

In February 2024, the township changed status to became a regular municipality and took the current name of Ristigouche-Sud-Est.

In the 2021 Census of Population conducted by Statistics Canada, Ristigouche-Sud-Est had a population of 170 living in 81 of its 95 total private dwellings, a change of -0.6% from its 2016 population of 171. With a land area of 51.76 km (19.98 sq mi), it had a population density of 3.3/km (8.5/sq mi) in 2021.

Historical Census Data - Ristigouche-Sud-Est, Quebec

Year Pop. ±% 1911 285 —     1921 357 +25.3% 1931 312 −12.6% 1941 371 +18.9% 1951 288 −22.4% 1956 271 −5.9% 1961 170 −37.3%	Year Pop. ±% 1966 159 −6.5% 1971 145 −8.8% 1976 194 +33.8% 1981 155 −20.1% 1986 145 −6.5% 1991 154 +6.2% 1996 155 +0.6%	Year Pop. ±% 2001 165 +6.5% 2006 173 +4.8% 2011 167 −3.5% 2016 171 +2.4% 2021 170 −0.6%
Source: Statistics Canada

Canada Census Mother Tongue - Ristigouche-Sud-Est, Quebec
Census		Total		French				English				French & English				Other
Year		Responses		Count	Trend	Pop %		Count	Trend	Pop %		Count	Trend	Pop %		Count	Trend	Pop %
2021		170		130	0.0%	76.5%		35	12.5%	20.6%		5	n/a%	2.9%		0	100.0%	0.0%
2016		175		130	4.0%	74.3%		40	14.3%	22.9%		0	100.0%	0.0%		5	n/a%	2.9%
2011		165		125	7.4%	75.8%		35	16.7%	21.2%		5	50.0%	3.0%		0	0.0%	0.0%
2006		170		135	8.0%	79.4%		30	14.3%	17.6%		10	n/a%	5.9%		0	0.0%	0.0%
2001		165		125	47.1%	75.8%		35	30.0%	21.2%		0	0.0%	0.0%		0	0.0%	0.0%
1996		140		85	n/a	60.7%		50	n/a	35.7%		0	n/a	0.0%		0	n/a	0.0%

Municipal council (as of 2024):

• Mayor: David Ferguson
• Councillors: Daniel Charest, Lucien Leblanc, Francis Levesque, Marie-Ève Nadeau, Sabrina Landry-Court, Mélanie Côté

• List of anglophone communities in Quebec
• List of municipalities in Quebec

• Restigouche South-East Municipality (French)