Guelph Lake is a man-made reservoir on the Speed River, in the Township of Guelph/Eramosa. It is located upriver and slightly northeast of the city of Guelph, Ontario. The reservoir was created in 1974, with the construction of the Guelph Lake dam. The site is part of a 1,608 hectare (3,971 acre) conservation area maintained by the Grand River Conservation Authority.