The Mokelumne River is a 95-mile -long river in northern California in the United States. The river flows west from a rugged portion of the central Sierra Nevada into the Central Valley and ultimately the Sacramento–San Joaquin River Delta, where it empties into the San Joaquin River-Stockton Deepwater Shipping Channel. Together with its main tributary, the Cosumnes River, the Mokelumne drains 2,143 square miles in parts of five California counties. Measured to its farthest source at the head of the North Fork, the river stretches for 157 miles .
The river is colloquially divided into the Upper Mokelumne River, which stretches from the headwaters to Pardee Reservoir in the Sierra foothills, and the Lower Mokelumne River, which refers to the portion of the river below Camanche Dam. In its lower course, the Mokelumne is used heavily for irrigation and also provides water for the east San Francisco Bay Area through the Mokelumne Aqueduct. Several major tributaries of the river have been developed for the generation of hydroelectric power.
The name is Plains Miwok and is constructed from moke, meaning fishnet, and -umne, a suffix meaning "people of". The town of Mokelumne Hill was named for the river in about 1850.