Riverside County is a county in the U.S. state of California. One of 58 California counties, it covers 7,208 sq mi (18,669 km2) in the southern part of the state, and stretches from Orange County to the Colorado River, which forms the state border with Arizona. The county derives its name from the city of Riverside, which is the county seat. Along with neighboring San Bernardino County, the two counties have been dubbed the 'Inland Empire'.
The population of Riverside County was 2,189,641 in 2010.