- Oakwood Park
- Oasis
- Oasis Mobile Home Park
- Oates
- Ocie
- Octa
- Odessa
- Odin
- Oermann
- Oetters
- Ogborn
- Ogden
- Oglesville
- Ohio
- Ohlman
- Oil City
- Okete
- Olathia
- Old Appleton
- Old Bland
- Old Chilhowee
- Old Jamestown
- Old Linn Creek
- Old Merritt
- Old Mines
- Old Monroe
- Old North Saint Louis
- Old Pattonsburg
- Old Peculiar
- Old Success