- Osborns Store
- Osceola
- Osso
- Othma
- Otter Hill
- Otterburn
- Otterdale
- Otterdam Mobile Home Park
- Otterview Gardens
- Otterville
- Ottobine
- Ottoman
- Ottoway
- Outlaw Mobile Home Park
- Overall
- Overlee Knolls
- Overlook Heights
- Overton
- Owen Corner
- Owens
- Owens
- Owens
- Owens Store
- Owensville
- Owenton
- Owl Trap
- Oxford
- Oxford Furnace
- Oxfordshire
- Oyster