- Oak Forest
- Oak Grove
- Oak Grove
- Oak Hill
- Oak Lodge
- Oak Park
- Oak Tree Crossroads
- Oakdale
- Oakdale
- Oakford
- Oakland City
- Oakland City Junction
- Oaklandon
- Oakley
- Oaktown
- Oakville
- Oakwood
- Oakwood
- Oakwood Mobile Home Park
- Oakwood Park
- Oatsville
- Ober
- Occident
- Ockley
- Octagon
- Odell
- Odon
- Ogden
- Ogden Dunes
- Ogden Island