Topanga is an unincorporated community in western Los Angeles County, California, United States. Located in the Santa Monica Mountains, the community exists in Topanga Canyon and the surrounding hills. The narrow southern portion of Topanga at the coast is between the city of Malibu and the Los Angeles neighborhood of Pacific Palisades. As of the 2020 census the population of the Topanga CDP was 8,560. For statistical purposes, the United States Census Bureau has defined Topanga as a census-designated place (CDP). The ZIP code is 90290 and the area code is primarily 310, with 818 only at the north end of the canyon. It is in the 3rd County Supervisorial district.

The Tongva language is an extinct Uto-Aztecan language formerly spoken by the Tongva, a Native American people who have lived in and around modern day Los Angeles for centuries. It has not been a language of everyday conversation since the 1940s. The Gabrielino people now speak English but a few are attempting to revive their language by using it in everyday conversation and ceremonial contexts. Presently, Gabrielino is also being used in language revitalization classes and in some public discussion regarding religious and environmental issues. Tongva is closely related to Serrano. The names of several cities and neighborhoods in Southern California are of Tongva origin, and include Pacoima, Tujunga, Topanga, Azusa, Cahuenga in Cahuenga Pass and Cucamonga in Rancho Cucamonga.