The Montreal River has an inverted check mark shape, first flowing north east, then south east to its mouth. It begins at Smoothwater Lake in Lady Evelyn-Smoothwater Provincial Park. Ishpatina Ridge, the highest point in Ontario, lies in the Montreal River drainage basin just south of Smoothwater Lake, and separates the headwaters of the Montreal River proper, to the northwest, and the headwaters of the tributary Lady Evelyn River, which joins far downstream, to the southeast.