Topanga is a census-designated place in western Los Angeles County, California, United States. Located in the Santa Monica Mountains, the community lies in Topanga Canyon. The narrow southern portion of Topanga at the coast is in between the city of Malibu and the city of Los Angeles neighborhood of Pacific Palisades. Topanga had a population of 8,289 as of 2010. 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.