Saint-Roch-de-l'Achigan is a Quebec municipality located in the Montcalm Regional County Municipality located in the Lanaudière region. It is on the banks of the Achigan River, a tributary of the L'Assomption River. According to the town's website, the population is approximately 5,400 and growing steadily as a result of the suburban sprawl in the North Shore of Greater Montreal.

The first settlers arrived near the 1770s and built a flour mill on a township located alongside the Rivière de l'Achigan. The area was located on the northern edges of the first developed lands that were located along both sides of the Saint Lawrence River. In 1787, the Saint-Roch-de-l'Achigan Parish was formed and in 1832, its post office opened, three years after the construction of its first school. In 1845, the parish municipality was established. It was abolished in 1847 when it became part of the County Municipality of Lachenaie, but was reestablished in 1855 as the Parish Municipality of Saint-Roch.

In 1921, Saint-Roch lost a part of its territory when the Municipality of Saint-Roch-Ouest was formed. In 1957, it regained its original name when "de-l'Achigan" was added in order to distinguish it from other places named "Saint-Roch". In 2006, it changed statutes and became the Municipality of Saint-Roch-de-l'Achigan.

Population trend:

• Population in 2021: 5,453 (2011 to 2016 population change: 5.2%)
• Population in 2016: 5,147 (2011 to 2016 population change: 5.2%)
• Population in 2011: 4,892 (2006 to 2011 population change: 10.0%)
• Population in 2006: 4,449
• Population in 2001: 4,164
• Population in 1996: 4,305
• Population in 1991: 3,795
• Population in 1986: 3,535
• Population in 1981: 3,436
• Population in 1976: 3,063
• Population in 1971: 2,721
• Population in 1966: 2,316
• Population in 1961: 2,109
• Population in 1956: 1,910
• Population in 1951: 1,782
• Population in 1941: 1,632
• Population in 1931: 1,440
• Population in 1921: 1,718
• Population in 1911: 2,200
• Population in 1901: 1,841
• Population in 1891: 2,048
• Population in 1881: 2,290
• Population in 1871: 2,523
• Population in 1861: 2,784

Private dwellings occupied by usual residents: 2,165 (total dwellings: 2,226)

Mother tongue:

• English as first language: 1.2%
• French as first language: 96.3%
• English and French as first language: 0.8%
• Other as first language: 1.3%

The town is accessible via Autoroute 25 which links Laval and Montreal towards the northeastern suburbs including Terrebonne and Mascouche. Since the Olivier-Charbonneau Bridge connecting Montreal and Laval was opened to traffic in 2011, it also has a direct link to the south shore of Montreal and Autoroutes 20 and 40. The municipality is located near the northern terminus of the Autoroute which continues further north via Route 125 towards the Mont-Tremblant Provincial Park north of Saint-Donat and Rawdon.

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Commission scolaire des Samares operates francophone public schools:

• École secondaire de l'Achigan
• École Notre-Dame

The Sir Wilfrid Laurier School Board operates anglophone public schools, including:

• Joliette Elementary School in Saint-Charles-Borromée
• Joliette High School in Joliette

• List of municipalities in Quebec

• Website of the Municipality