- Oxlip
- Oakland Estates Mobile Home Park
- Olson's Mobile Home Park
- Orth
- Oslund
- Oak Ridge Trailer Court
- Oak Center
- Oakbury
- Otisville
- Oakridge
- Oster
- O'Dell Island
- Oak Island
- Oaks Corner
- Opstead
- Oak Park
- Oakland
- Orleans
- Osage
- Otisco
- Ottawa
- Outing
- Oylen
- Owanka
- Oshawa
- Oak Park Heights
- Oakport
- Ogilvie
- Okabena
- Oklee