Castaic is an unincorporated community and census designated place in the northwestern part of Los Angeles County, California, United States. As of the 2010 census it had a population of 19,015.
Tens of thousands of motorists pass through Castaic daily as they drive to or from Los Angeles on Interstate 5. Castaic Lake is part of the California Water Project and is the site of a hydro-electric power plant. Castaic is 38 miles northwest of Los Angeles Union Station and northwest of the city of Santa Clarita.
