Belmont is a city in San Mateo County, California, United States. It is a small suburb in the San Francisco Bay Area, located half-way down the San Francisco Peninsula between San Mateo and San Carlos. The population was 25,123 at the 2000 census. Belmont apartments for rent comparison page shows most up to date rent information on Belmont apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.