The Petawawa River is a river in eastern Ontario, Canada.

It starts in northern Algonquin Park and flows east, emptying into the Ottawa River at Petawawa. The river is 187 km in length and drains an area of 4,200 km².

The river's name comes from the Algonquian language, meaning "where one hears a noise like this", which refers to its many rapids. From the late 1800s until the 1960s, the river was used to transport lumber from the forested areas surrounding the river. The river is popular among canoeing and kayaking enthusiasts for its white water rapids and often spectacular views.

Tributaries of this river include the:

• Barron River
• Crow River
• Little Madawaska River
• Nipissing River
• North River