Saint-Léon-le-Grand (French pronunciation: [sɛ̃ leɔ̃ lə ɡʁɑ̃]) is a parish municipality in the Maskinongé Regional County Municipality in the Mauricie region of the province of Quebec, Canada.

In the 2021 Census of Population conducted by Statistics Canada, Saint-Léon-le-Grand had a population of 863 living in 369 of its 393 total private dwellings, a change of -7% from its 2016 population of 928.

With a land area of 75.97 km2 (29.33 sq mi), it had a population density of 11.4/km2 (29.4/sq mi) in 2021.

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