The Smith River is a river on the Pacific coast of Northern California in the United States, approximately 20 miles (32 km) long. It drains a rugged area of the Coast Ranges west of the Siskiyou Mountains just south of the Oregon border and north of the watershed of the Klamath River. It is the largest river system in California that flows freely along its entire course. It was named for the explorer, Jedediah Smith.

It is formed by the confluence of its Middle and South forks in Del Norte County, in the extreme northwest corner of California. The Middle Fork (25 mi/40 km) rises in northeastern Del Norte County, approximately 30 miles (48 km) ENE of Crescent City and flows southwest. The South Fork (20 mi/32 km) rises in southern Del Norte County, approximately 25 miles (40 km) southeast of Crescent City, and flows north. The forks join in central Del Norte County and flow generally northwest, entering the Pacific near the village of Smith River, approximately 10 mi (16 km) north of Crescent City.