The Feather River is the principal tributary of the Sacramento River, in the Sacramento Valley of Northern California. The river's main stem is about long. Its length to its most distant headwater tributary is about . Its drainage basin is about . The main stem Feather River begins in Lake Oroville, where its four long tributary forks join together—the South Fork, Middle Fork, North Fork, and West Branch Feather Rivers. These and other tributaries drain part of the northern Sierra Nevada, and the extreme southern Cascades, as well as a small portion of the Sacramento Valley. The river's drainage basin above Lake Oroville is , or about 53% of the whole.