Belmont is a city in San Mateo County, California, United States. It is in the San Francisco Bay Area, located half-way down the San Francisco Peninsula between San Mateo and San Carlos. It was originally part of the Rancho de las Pulgas, for which one of its main roads, the Alameda de las Pulgas, is named. The town was incorporated in 1926. The population was 25,835 at the 2010 census.