- Onion Creek
- Onslow
- Ophir
- Orcas Island
- Orchard Bluff Mobile Home Park
- Orchard Grove
- Orchard Heights
- Orchard Prairie
- Orchard Trailer Park
- Orchards North
- Orchards South
- Orient
- Orillia
- Orin
- Orondo
- Osborn Corner
- Osborne
- Osborne Corner
- Osceola
- Oskams Corner
- Ostrander
- Otis Orchards
- Otis Orchards-East Farms
- Outlook
- Overlake
- Ovington
- Oxley
- Oyehut
- Oyehut-Hogans Corner
- Oysterville