- Oak Center
- Oak Creek
- Oak Grove
- Oak Hall
- Oak Hill
- Oak Hill Mobile Home Park
- Oak Island
- Oak Knoll
- Oak Knoll
- Oak Orchard
- Oak Park Terrace
- Oak Ridge Estates
- Oak Ridge Village Mobile Home Park
- Oakdale
- Oakdale Estates
- Oakfield
- Oakland
- Oakland
- Oakland Heights
- Oakley
- Oakridge
- Oakwood
- Oakwood
- Oakwood Mobile Home Community
- Oconomowoc
- Oconomowoc Lake
- Oconto
- Oconto Falls
- Odanah
- Ogdensburg