Cities, Towns, Neighborhoods & Other Populated Places in California.
| City Name | Title | County | Population |
|---|---|---|---|
| Oakland | Port city and county seat of Alameda County, California, United States | Alameda | 433,031 |
| Oxnard | City in Ventura County, California, United States | Ventura | 208,881 |
| Ontario | City located in south west San Bernardino County, California, United States | San Bernardino | 185,010 |
| Oceanside | City in California, United States | San Diego | 175,742 |
| Orange | City in California, United States | Orange | 138,669 |
| Oakley | City in California | Contra Costa | 42,543 |
| Orcutt | Census designated place | Santa Barbara | 35,262 |
| Oakdale | City in Stanislaus County, California, United States | Stanislaus | 23,596 |
| Oroville | County seat of Butte County, California, USA | Butte | 20,737 |
| Orinda | City in California, USA | Contra Costa | 19,926 |
| Orland | Municipality in Trøndelag, Norway | Glenn | 10,323 |
| Orange Cove | City | Fresno | 10,273 |
| Ojai | City in California, United States | Ventura | 7,470 |