O
- Oak View
- Oakdale
- Oakhurst
- Oakland
- Oakley
- Occidental
- Oceanside
- Ocotillo
- Ojai
- Olancha
- Old Station
- Olema
- Olivenhain
- Olympic Valley
- Ontario
- Orange
- Orange Cove
- Orangevale
- Orcutt
- Orick
- Orinda
- Orland
- Orleans
- Orosi
- Oroville
- Oxnard
Read more about this topic: List Of Communities In California