- Ormand
- Owl
- Oak Glen
- Oak Hills
- Old Dale
- Oak Grove
- Ocean Hills
- Orford
- Osaka Island
- Oak Park
- Oak Shores
- Oaks
- Oceano Beach
- Old Adobe
- Old Town
- Orchams
- Ortega
- Ogilvie Island
- Old Gilroy
- Old Mill Park Mobile Home Park
- Olympia
- Orchard Lane Mobile Home Park
- Obie
- Olinda
- Osborne
- Oxford Mill
- Oak Ridge Mobile Estates
- Oakbar
- Oaks Mobile Home And Recreational Vehicle Park
- Oro Fino