- Onamia
- Ormsby
- Oronoco
- Orr
- Osakis
- Osseo
- Ottertail
- Owatonna
- Org
- Oak Terrace Estates
- Oronoco Estates
- Oak Manor Mobile Home Village
- Oak View Mobile Home Park
- Oak Island
- Okorb Island
- Old Mesaba
- Oliver Island
- Olson's Mobile Home Park
- One Tree Island
- Onega
- Oneota
- Ormonds Island
- Olga
- Oaks Mobile Home Park
- Orrock
- Opole