O
- Oak Bluffs
- Oakdale
- Oak Grove Village
- Oakham
- Oak Hill Park
- Oakland
- Oakland Square
- Ocean Grove
- Oklahoma Heights
- Old City
- Old Common
- Olde English Village
- Old Harbor
- Old Hill
- Old North Ashburnham Station
- Old Silver Beach
- Onset
- Orange
- Orchard Hills Estates
- Orient Heights
- Orleans
- Osterville
- Otis
- Otis Res
- Otis Wood Lanes
- Otter River
- Overbrook
- Owen District
- Oxford