- Obi
- Oramel
- Oakwoods Mobile Home Court
- Occanum
- Occanum Falls Mobile Home Park
- Onoville
- Orlando
- Orchard Knoll
- Owens Mills
- Oakwood
- Omro
- Owasco
- Owasco Hill
- Owasco Lake Station
- Orchard Terrace
- Oriental Park
- Otselic
- Otselic Center
- Oak Hill Landing
- Old Chatham
- Omi
- Oak Meadows Mobile Home Park
- Oniontown
- Oakfield
- Onchiota
- Oppenheim
- Oregon
- Oak Hill
- Onteora Park
- Otter Hook