Coordinates: 32°58′23.01″N 117°14′57.57″W / 32.9730583°N 117.2493250°W
The San Dieguito River is a major river in Southern California, USA. Its headwaters rise on the southern slope of the Volcan Mountains in San Diego County and the river flows generally southwest for 23.8 miles (38.3 km), draining 346 square miles (900 km2) before emptying into the Pacific Ocean 20 miles (32 km) north of San Diego.
The river officially begins at the confluence of two streams, Santa Ysabel Creek and Santa Maria Creek, near the town of San Pasqual. Santa Ysabel Creek rises in the northeastern corner of the San Dieguito River watershed and flows west, creating Lake Sutherland. It then flows out of the lake's dam and westwards for the rest of its course. Its total length is about 11 miles (18 km). Santa Maria Creek, the smaller of the two streams, begins near the city of Ramona and flows northwards about 7 miles (11 km) through the Ramona Grasslands and Bandy Canyon. A third fork, Temescal Creek, rises in the Cleveland National Forest near Lake Henshaw and flows south about 9 miles (14 km) into Santa Ysabel Creek.