St Marys River, one of the largest rivers in Nova Scotia, flows into the Atlantic Ocean at a point 190 km E of Halifax. It offers excellent opportunities for sportfishing, especially for Atlantic salmon and a char, locally called "sea trout." Salmon, in particular, are noted for their heavy runs in spring and early summer.

Early French fur traders gave the river its name and in 1655 established a post at Fort Sainte Marie, where the town of Sherbrooke now stands. In addition to the fishing industry, the river is used to transport quantities of pulpwood downstream from Sherbrooke.