A historical region and province of British North America on the upper St. Lawrence River and the Great Lakes, roughly coextensive with southern Ontario, Canada. Formed in 1791 from the western half of the Province of Quebec (1763–1791), it joined Lower Canada in 1841 to form the Province of Canada (1841–1867).
- (historical) A former British colony located in what is now southern Ontario.
From its position on the Saint Lawrence River. See Canada.