Montclair is a city in San Bernardino County, California, United States. Montclair is bordered by Pomona to the West, Claremont and Upland to the North, Ontario to the East and unincorporated San Bernardino County (near Chino) to the South. Montclair is in the Pomona Valley and part of the Inland Empire region in the Greater Los Angeles Area. The San Bernardino Freeway (10 Fwy.) runs through the northern part of the city.