Pinole is a city in Contra Costa County, California, United States. The population was 18,390 at the 2010 census.
The name derives from "pinole", a Nāhuatl word for a kind of flour made from the seeds of maize, chia, and various other grasses and annual herbs. An expedition under Pedro Fages was said to have run out of provisions while exploring the area, and to have been fed pinole by a local village, and so the Spaniards named their camp "El Pinole".
In 1823, Ygnacio Martinez, commandant of the Presidio of San Francisco, received a land grant of Rancho El Pinole from the Mexican government. Martinez built a hacienda in Pinole Valley at the present side of Pinole Valley Park. During the 1850s, Bernardo Fernandez, a Portuguese immigrant, started a trading facility on the shores of San Pablo Bay and eventually built the historic Fernandez Mansion, which still stands today at the end of Tennent Avenue. From these early beginnings, a small but thriving community grew into the city now known as Pinole.
The settlement grew with the coming of the Southern Pacific Railroad in 1878 and the establishment of the California Powder Works in nearby Hercules. During this period, this city had an active waterfront and was a regional commercial and banking center.