The 65.0-mile-long (104.6 km) [3] South Yuba River is a left-entering tributary of the Yuba River originating in the northern Sierra Nevada at Lake Angela in Nevada County about three quarters of a mile north of Donner Pass, about three miles east of the town of Soda Springs.

After passing through Lake Van Norden with Upper Castle Creek (longer than the Lake Angela stem) entering from the right, it gathers numerous snow-fed tributaries running west through a marshy, lake-filled valley, criss-crossing Interstate 80.

The river briefly enters Placer County, then flows into Lake Spaulding, then plunges westward into a steep-sided valley.

Its mouth is on the east shore of upper Englebright Lake, formed by a dam across the Yuba River.

[4] The California Office of Environmental Health Hazard Assessment has issued a safe eating advisory for any fish caught in South Yuba River due to elevated levels of mercury and PCBs.