Green Peter Reservoir is a reservoir created by Green Peter Dam on the Middle Santiam River 11 miles (18 km) northeast of Sweet Home, Oregon, United States. The reservoir is approximately 10 miles (16 km) long and has a surface area of approximately 3,720 acres (1,510 ha) when full. The reservoir is used for hydropower, recreation, flood risk management, water quality, irrigation, and as a fish and wildlife habitat.

This large reservoir is within an easy drive of the Willamette Valley, primarily is best known as western Oregon’s premier kokanee fishing lake.

Green Peter is located at about 1,000 feet in elevation in the foothills of the Cascade Mountains.