South Branch Ontonagon River
General data
- Name: South Branch Ontonagon River
- Water system: St. Lawrence River
- Water type: River
- Progression: West Branch Ontonagon River -> Ontonagon River -> Lake Superior -> St. Marys River (Michigan–Ontario) -> Lake Huron -> St. Clair River -> Lake St. Clair (North America) -> Detroit River -> Lake Erie -> Niagara River -> Lake Ontario -> St. Lawrence River -> Gulf of St. Lawrence -> Atlantic Ocean -> Planet Earth
- Climates: Continental
- Continents: North America
- Countries: United States of America
The South Branch Ontonagon River is formed in southwestern Ontonagon County by the confluence of the short Tenmile Creek and the Cisco Branch Ontonagon River. The Cisco Branch starts in Cisco Lake in eastern Gogebic County and flows generally north-northeastwardly for 32.7 miles (52.7 km) to the South Branch, which then flows northwardly for 33.3 miles (53.6 km), passing the community of Ewen, to join the West Branch.