- Odessa
- Oroville
- Oakville
- Oak Harbor
- Oakesdale
- Ocean City
- Ocean Park
- Ocean Shores
- Okanogan
- Olympia
- Omak
- Opportunity
- Orcas
- Orchards
- Orting
- Oso
- Othello
- O'Brien
- O'Neal Island
- Oak Acres Mobile Home Park
- Oak Hollow Mobile Home Park
- Oak Island
- Oak Park
- Oak Point
- Oakland
- Oakridge Manor Mobile Home Park
- Oaks Mobile Home Park
- Obstruction Island
- Ocean Grove
- Ocean View Mobile Home Park