- Obelisk
- Oberlin
- Oberlin Gardens
- Ochre Mill
- Odell
- Odin
- Odle Corners
- Ogdensburg
- Ogdonia
- Ogle
- Ogletown
- Ohiopyle
- Ohioview
- Ohioville
- Ohl
- Oil City
- Oil City
- Okehocking Hills
- Oklahoma
- Oklahoma
- Okome
- Olanta
- Old Boston
- Old Clarendon
- Old Colonial Village
- Old Concord
- Old Covered Bridge Estates
- Old Crabtree
- Old Ferry
- Old Forge