Casselman is a village in eastern Ontario, Canada, in the United Counties of Prescott and Russell. Situated on the South Nation River about 55 km (34 mi) southeast of downtown Ottawa, along the Trans-Canada Highway 417. It is served by a station on the Montreal-Ottawa Via Rail train, twice a day in each direction.

Casselman is surrounded on all sides by The Nation since Casselman citizens refused to join the fusion of municipalities.

The village was named after Martin Casselman who built a sawmill near the site of the current town in 1844. Its post office was established in 1857. The village installed modern water and sewer services that became operational in 1977.

Casselman hosted L'écho d'un peuple, at Ferme Drouin, one of the biggest shows ever presented in Ontario, until the organization ran into financial trouble in 2008.

In the 2021 Census of Population conducted by Statistics Canada, Casselman had a population of 3,960 living in 1,578 of its 1,630 total private dwellings, a change of 11.6% from its 2016 population of 3,548. With a land area of 5.13 km (1.98 sq mi), it had a population density of 771.9/km (1,999.3/sq mi) in 2021.

Mother tongue:

• French as first language: 79.3%
• English as first language: 17.4%
• English and French as first language: 1.9%
• Other as first language: 1.4%

• Transit Eastern Ontario operates under the authority of The North Glengarry Prescott Russell (NGPR) Transport Board
• List of francophone communities in Ontario

• Official website

45°18′N 75°05′W / 45.300°N 75.083°W / 45.300; -75.083