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 Mattawa River is a river in central Ontario, Canada. It flows east from Trout Lake east of North Bay and enters the Ottawa River at the town of Mattawa. Counting from the head of Trout Lake, it is 76 kilometres (47 mi) long. The river's name comes from the Algonquin word for "meeting of waterways".