- Orchard Lane Trailer Court
- Orchard Mobile Home Park
- Orchard View
- Oregon Corners
- Oregonia
- Oreton
- Oreville
- Orland
- Orpheus
- Orrville Trailer Park
- Osage
- Osborn Corners
- Osceola
- Osterholt Mobile Home Park
- Otsego
- Otsego
- Otter
- Otter Island
- Otterbein
- Otterbein
- Otterbein
- Ottokee
- Ottokee Station
- Outville
- Oval City
- Over-The-Rhine
- Overlook Hills
- Overlook Trailer Park
- Overpeck
- Overton