The Nacimiento River is a 64.8-mile-long (104.3 km) river in southern Monterey County and northern San Luis Obispo County, California. A large portion of the river's run is on military reservations. The river's upper reaches are inside Fort Hunter Liggett, Lake Nacimiento is in the middle and the lower reaches are inside Camp Roberts. It is the largest tributary of the Salinas River in terms of streamflow.