| Onekama Township, MI (Township) |
| Oneonta, NY (City) |
| Oneonta, AL (City) |
| Oneonta, NY (Town) |
| Oneota, SD (Township) |
| Ong, NE (Village) |
| Onida, SD (City) |
| Onley, VA (Town) |
| Onondaga, NY (Town) |
| Onondaga County, NY (County) |
| Onondaga Township, MI (Township) |
| Onota Township, MI (Township) |
| Onslow, IA (City) |
| Onslow County, NC (County) |
| Onstad, MN (Township) |
