San Lucas is an unincorporated community and census-designated place in Monterey County, California, United States. It was founded in 1886 and named after the Rancho San Lucas, which was granted in 1842. The post office was first established in 1892. San Lucas is located in the Salinas Valley, on the Salinas River 8 miles southeast of King City, at an elevation of 410 feet. The population was 324 at the 2020 census, up from 269 in 2010.