- Owen District
- Oak Grove
- Oak Hill Park
- Oaklands
- Old Cambridge
- Old City
- Oakdale
- Old Boat Point
- Old Spain
- Overbrook
- Oakdale
- Oakland Square
- Ocean Bluff
- Ocean Bluff-Brant Rock
- Old Mouth North River
- Old Oaken Bucket Homestead
- Old Sow
- Oldham Pines
- Oldham Village
- Onset Island
- Onset Station
- Osceola Island
- Outer Seal Rock
- Outer Tautog Rock
- Oak Island
- Orient Heights
- Outer Brewster Island
- Oak Hill
- Oak Island
- Oakdale