Belmont is a city in San Mateo County in the U.S. state of California. It is in the San Francisco Bay Area, on the San Francisco Peninsula about halfway between San Francisco and San Jose. It was originally part of Rancho de las Pulgas, for which one of its main roads, the Alameda de las Pulgas, is named. The city was incorporated in 1926. Its population was 25,835 at the 2010 census.

Ralston Hall is a historic landmark built by Bank of California founder William Chapman Ralston on the campus of Notre Dame de Namur University, and is also home to Notre Dame High School. It was built around a villa formerly owned by Count Leonetto Cipriani [fr], an Italian aristocrat. The locally famous “Waterdog Lake” is also located in the foothills and highlands of Belmont.

A surviving structure from the Panama-Pacific International Exposition is on Belmont Avenue (another is the Palace of Fine Arts in San Francisco). The building was brought to Belmont by E.D. Swift shortly after the exposition closed in 1915.

Belmont has a smoking ordinance passed in January 2009 which bans smoking in all businesses and multi-story apartments and condominiums; the ordinance has been described as one of the strictest in the nation.