- Oaksville
- Oakvale
- Oakville
- Oakwood
- Oakwood
- Oakwood Beach
- Oakwood Estates Mobile Home Park
- Oakwood Heights Station
- Oakwood Terrace
- Oakwoods Mobile Home Court
- Oatka
- Obernburg
- Obi
- Occanum
- Occanum Falls Mobile Home Park
- Ocean Bay Park
- Ocean Point
- Oceola Lake
- Odell
- Odell Islands
- Ogden Center
- Ogden Island
- Ohio
- Ohioville
- Oklahoma Beach
- Old Central Bridge
- Old Chatham
- Old City
- Old Field Mobile Home Park
- Old Forge