river rising in the Klamath Mountains, near Mount Shasta (Shasta, Mount) (in Siskiyou county), northern California, U.S. The river flows 382 miles (615 km) south-southwest between the Cascade (Cascade Range) and Sierra Nevada ranges, through the northern section (Sacramento Valley) of the Central Valley. It forms a common delta with the San Joaquin River before entering Suisun Bay, the northern arm of San Francisco Bay. Its principal tributaries are the Pit, McCloud, Feather, and American rivers. Total drainage area is about 27,100 square miles (70,200 square km); average annual runoff is 22 million acre-feet (27 billion cubic metres).

Shasta, Keswick, and Oroville (Oroville Dam) dams are key features of the Central Valley and Feather River irrigation and power projects, which serve southern portions of the state. California's largest river, the Sacramento is navigable for 256 miles (412 km) and accommodates oceangoing vessels as far as the city of Sacramento.

The name Sacramento was originally given to the Feather River by Gabriel Moraga in 1808; it was later applied to the main channel (originally called Rio de San Francisco). Scene of the Gold Rush of 1849, the river flows through one of the world's richest agricultural regions. The river harbours hundreds of species of fish, and the Sacramento River National Wildlife Refuge, in several units, protects several ecosystems.