- Odom
- Oenaville
- Ogburn
- Ogden
- Ogden
- Ogden
- Ogg
- Oglesby
- Ohio
- Oil City
- Oilla
- Oilton
- Ojo de Angua
- Oklahoma
- Oklahoma Flat
- Oklahoma Lane
- Oklaunion
- Okra
- Ola
- Olcott
- Old Airport Road Colonia
- Old Beekley Place
- Old Boston
- Old Brazoria
- Old Burk Place
- Old Caseyville Crossing
- Old Center
- Old Christian Place
- Old Corbett Place
- Old Davy