| Oakwood Hills, IL (Village) |
| Oakwood Park, MO (Village) |
| Oakwood Township, IL (Township) |
| Oasis Town, WI (Town) |
| Oberlin, OH (City) |
| Oberlin, KS (Township) |
| Oberlin, KS (City) |
| Oberlin, LA (Town) |
| Oberon, ND (Township) |
| Oberon, ND (City) |
| Obert, NE (Village) |
| Obetz, OH (Village) |
| Obion, TN (Town) |
| Obion County, TN (County) |
| Oblong, IL (Village) |
