Barrios de California O
- Oak Creek
- Oak Knoll Golf Links
- Oak Knoll-Redwood Park
- Oak Park
- Oak Park
- Oak View
- Oakridge
- Ocean Crest
- Ocean Hills
- Ocean Park
- Oceana
- Ohlone
- Oildale
- Old Davis North
- Old East Davis
- Old North Sacramento
- Old Sacramento
- Old San Leandro
- Old Town
- Old Town
- Old Town Kern
- Olde Torrance Neighborhood
- Oleander/Sunset
- Olive Drive
- Olive Drive Area
- Olive Heights
- Olympia
- Olympus Pointe
- Orange Heights
- Orange Park
- Ortega Park
- Otay Mesa
- Otay Mesa West
- Otay Ranch
- Otay Ranch Village
- Otay Town
- Outer Monterey
- Outer Sunset
- Oxnard Shores