The Diablo Valley refers to a valley in the East Bay of the San Francisco Bay Area, to the west/northwest of Mount Diablo.

[1] The valley contains the cities of Clayton, Concord, Martinez, Pleasant Hill (home to Diablo Valley College), most of Walnut Creek (The southern end is a part of the San Ramon Valley) and the CDP of Pacheco.

The Diablo Valley has a diverse population both ethnically, and socio-economically.

West of the Diablo Valley lies the Briones Regional Park and the Lamorinda area.

This Contra Costa County, California–related article is a stub.