Castroville is a census-designated place (CDP) in Monterey County, California, United States. At the time of the 2010 census the population was 6,481.
The site of the community was originally part of Rancho Bolsa Nueva y Moro Cojo, a 30,901-acre (125.05 km2) Mexican land grant given in 1844 by Manuel Micheltorena, Governor of Alta California, to María Antonia Pico de Castro. After the 1848 cession of California to the United States following the Mexican–American War, Juan Bautista Castro, son of María Antonia Pico de Castro, founded Castroville in 1863.