- Oak Knoll
- Oak Orchard
- Oak Park Terrace
- Oak Ridge Estates
- Oak Ridge Village Mobile Home Park
- Oakdale Estates
- Oakland
- Oakland
- Oakland Heights
- Oakley
- Oakridge
- Oakwood
- Oakwood
- Oakwood Mobile Home Community
- Ogema
- Oil City
- Ojibwa
- Okauchee
- Okee
- Old Albertville
- Old Ashippun
- Old Deerfield
- Old Fort
- Old Lebanon
- Old Scribbler Island
- Olivet
- Olmstead Island
- Olympic Village
- Onaway Island
- Ondaig Island