Oakley is a city in Contra Costa County, California, United States. It is within the nine-county San Francisco Bay Area. The population at the 2020 United States census was 43,357. Oakley was incorporated in 1999, making it the newest incorporated city in Contra Costa County.

Contra Costa County is a county located in the U.S. state of California, in the East Bay of the San Francisco Bay Area. As of the 2020 United States Census, the population was 1,165,927. The county seat is Martinez. It occupies the northern portion of the East Bay region of the San Francisco Bay Area and is primarily suburban. The county's name refers to its position on the other side of the bay from San Francisco. Contra Costa County is included in the San Francisco–Oakland–Berkeley, CA Metropolitan Statistical Area.