Montclair is a city in the Pomona Valley, in southwestern San Bernardino County, California. The population was 36,664 in the 2010 United States Census. Montclair is bordered by Pomona to the west, Claremont and Upland to the north, Ontario to the east, and Chino to the south. Montclair is in the Pomona Valley and part of the Inland Empire region.
The San Bernardino Freeway (I-10) runs through the northern part of the city.