Santa Paula is a city in Ventura County, California, United States. Situated amid the orchards of the Santa Clara River Valley, the city advertises itself to tourists as the "Citrus Capital of the World". Santa Paula was one of the early centers of California's petroleum industry. The Union Oil Company Building, the founding headquarters of the Union Oil Company of California in 1890, now houses the California Oil Museum. The population was 30,657 at the 2020 census, up from 29,321 at the 2010 census.