- Orson Island
- Ossipee Mills
- Otis
- Otisfield Gore
- Otter Creek
- Otter Island
- Otter Island
- Otter Island
- Otter Island
- Otter Island
- Ouellette
- Outer Bar Island
- Outer Doctor Island
- Outer Head
- Outer Heron Island
- Outer Island
- Outer Island
- Outer Ram Island
- Overlake
- Overset Island
- Owls Head
- Oxbow
- Oxford
- Oxford Station