Mattawa is a town in northeastern Ontario, Canada at the confluence of the Mattawa and Ottawa Rivers in Nipissing District. The first Europeans to pass through this area were Étienne Brûlé and Samuel de Champlain.

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.