The Swanson River is a stream, 40 miles (64 km) long, on the Kenai Peninsula of south-central Alaska in the United States. Beginning at Gene Lake in the Swanson Lakes district, it flows southwest then north to Number Three Bay on the Gompertz Channel of Cook Inlet.The river's entire course lies within the Kenai National Wildlife Refuge. In its lower reaches, it passes through the Swanson River Oil Field east of Nikiski before turning sharply north.