Valencia is an unincorporated community in northwestern Los Angeles County, California, United States. The area, west of Interstate 5, is expanding with residential development and already includes major commercial and industrial parks. It straddles State Route 126 and the Santa Clara River.

The Santa Clara River is an 83 mi (134 km) long river in Ventura and Los Angeles counties in Southern California. It drains parts of four ranges in the Transverse Ranges System north and northwest of Los Angeles, then flows west onto the Oxnard Plain and into the Santa Barbara Channel of the Pacific Ocean.