Stevenson Ranch is an unincorporated community in the Santa Clarita Valley of Los Angeles County, California. Stevenson Ranch is set in the foothills of the Santa Susana Mountains and lies west of Interstate 5 and the city of Santa Clarita. Stevenson Ranch encompasses about 6.4 square miles (17 km2). About 1,000 acres (4.0 km2) are set aside as parks, recreation areas, and open space. A master-planned community, it was approved by the county in 1987. The population was 20,178 at the time of the 2020 census. For statistical purposes, the Census Bureau has designated it a census-designated place (CDP).

The Santa Clarita Valley (SCV) is part of the upper watershed of the Santa Clara River in Southern California. The valley was part of the 48,612-acre (19,673 ha) Rancho San Francisco Mexican land grant. Located in Los Angeles County, its main population center is the city of Santa Clarita which includes the neighborhoods of Canyon Country, Newhall, Saugus, and Valencia. Adjacent unincorporated communities include Castaic, Stevenson Ranch, Val Verde, and Valencia.