The Klamath River flows 257 miles (414 km) through Oregon and northern California in the United States, emptying into the Pacific Ocean. By average discharge, the Klamath is the second largest river in California after the Sacramento River. Its nearly 16,000-square-mile (41,000 km2) watershed stretches from the high desert of south-central Oregon to the temperate rainforest of the North Coast. Unlike most rivers, the Klamath begins in a desert region and flows through the rugged Cascade Range and Klamath Mountains before reaching the ocean; National Geographic magazine has called the Klamath "a river upside down".

Karuk or Karok is the traditional language of the Karuk people in the region surrounding the Klamath River, in Northwestern California. The name ‘Karuk’ is derived from the Karuk word káruk, meaning “upriver”.