| Onstad, MN (Township) |
| Onsted, MI (Village) |
| Ontario, CA (City) |
| Ontario, OH (City) |
| Ontario , SD (Township) |
| Ontario, NY (Town) |
| Ontario, OR (City) |
| Ontario, ND (Township) |
| Ontario County, NY (County) |
| Ontario Township, IL (Township) |
| Ontario Village, WI (Village) |
| Ontelaunee Township, PA (Township) |
| Ontonagon, MI (Village) |
| Ontonagon County, MI (County) |
| Ontonagon Township, MI (Township) |
