Blue Creek is a 23-mile (37 km) long stream in the Northern Coast Ranges of California, and is the lowermost major tributary of the Klamath River. The creek begins in Elk Valley, in the Siskiyou Wilderness of the Six Rivers National Forest in Del Norte County. It flows southwest, receiving several major tributaries including the East Fork, Crescent City Fork, Nickowitz Creek, Slide Creek and the West Fork. It flows into the Klamath River in Humboldt County, 16 miles (26 km) upstream from where the Klamath empties into the Pacific Ocean.