The Portneuf River is a 124-mile-long (200 km) tributary of the Snake River in southeastern Idaho, United States. It drains a ranching and farming valley in the mountains southeast of the Snake River Plain. The city of Pocatello sits along the river near its emergence from the mountains onto the Snake River Plain.

Pocatello is the county seat and largest city of Bannock County, with a small portion on the Fort Hall Indian Reservation in neighboring Power County, in the southeastern part of the U.S. state of Idaho. It is the principal city of the Pocatello metropolitan area, which encompasses all of Bannock County.