| Ohiopyle, PA (Borough) |
| Ohioville, PA (Borough) |
| Ohiowa, NE (Village) |
| Ohlman, IL (Village) |
| Oil, IN (Township) |
| Oil City, LA (Town) |
| Oil City, PA (City) |
| Oil Creek Township, PA (Township) |
| Oil Trough, AR (Town) |
| Oilcreek Township, PA (Township) |
| Oilton, OK (City) |
| Ojai, CA (City) |
| Ojibwa Town, WI (Town) |
| Ojo Encino, NM (Tribal) |
| Okabena, MN (City) |
