Oak Park is an unincorporated community in southeastern Ventura County, California, United States. When developed in the Simi Hills in the late 1960s, a single road provided the only access to the community from Agoura Hills, California, in neighboring Los Angeles County. As of the 2020 census, Oak Park had a population of 13,898, up from 13,811 at the 2010 census. For statistical purposes, the United States Census Bureau has defined Oak Park as a census-designated place (CDP). The census definition of the area may not precisely correspond to local understanding of the area with the same name.