San Dimas is a city in the San Gabriel Valley of Los Angeles County, California, United States. As of the 2010 census, the city had a total population of 33,371. The city historically took its name from San Dimas Canyon in the San Gabriel Mountains above the northern section of present-day San Dimas. San Dimas derives its name from the Spanish name for Saint Dismas.

San Dimas is bordered by the San Gabriel Mountains range to the north, Glendora and Covina to the west, La Verne to its north and east side, Pomona to its south and east side, and Walnut to the southwest.