Lake Magog is a freshwater lake located in the Estrie region of Quebec, Canada. It is bordered by three municipalities: Sherbrooke, Magog and Sainte-Catherine-de-Hatley. Located in the Appalachian geological province, Lake Magog consists of sedimentary rock, especially slate and sandstone. Lake Magog is part of the watershed of the St. Francois River, which flows into the St. Lawrence River.