Lac Deschênes is a 44 kilometres long lake on the Ottawa River that runs from the Chats Falls Dam near Fitzroy Harbour in the west to the Deschênes Rapids at Britannia in the east. It is a little over 3.2 kilometres wide at its widest point and little more than a few hundred metres at its narrowest. The provincial border between Ontario and Quebec runs through the length of the lake with the City of Ottawa on its southern shore and the city of Gatineau on much of its northern shore.

The Ottawa River is a river in the Canadian provinces of Ontario and Quebec. It is named after the Algonquin word 'to trade', as it was the major trade route of Eastern Canada at the time. For most of its length, it defines the border between these two provinces. It is a major tributary of the St. Lawrence River and the longest river in Quebec.