The South Fork American River is a major tributary of the American River in El Dorado County, California, draining a watershed on the western slope of the Sierra Nevada east of Sacramento. The river begins in pristine Desolation Wilderness and flows through the Sierra Nevada foothills. The river at Coloma was the site of James Marshall's discovery of gold at Sutter's Mill on January 24, 1848, which started the California Gold Rush. The South Fork of the American is "the most popular recreation stream in the West" for whitewater rafting in North America, e.g., 80,000 visitors in 2011. Professional whitewater rafting companies have been offering commercial rafting trips on the South Fork American River since 1978.

The American River is a 30-mile-long (50 km) river in California that runs from the Sierra Nevada mountain range to its confluence with the Sacramento River in downtown Sacramento. Via the Sacramento River, it is part of the San Francisco Bay watershed. This river is fed by the melting snowpack of the Sierra Nevada and its many headwaters and tributaries, including the North Fork American River, the Middle Fork American River, and the South Fork American River.