Sea Ranch is an unincorporated community in Sonoma County, California, United States that was developed as a planned community beginning in the 1960s. It is known for its distinctive timber-frame structures designed by several noted American architects. The first unit built at Sea Ranch, Condominium One, was placed on the National Register of Historic Places in 2005. The community's ten-mile development played a role in the establishment of the California Coastal Commission. The population was 1,169 at the 2020 census. For statistical purposes, the United States Census Bureau has defined Sea Ranch as a census-designated place (CDP).