City | 2024 Population |
|---|---|
| Oak Harbor | 2,792 |
| Oak Hill | 1,395 |
| Oak Run | 512 |
| Oakwood | 537 |
| Oberlin | 7,410 |
| Obetz | 7,453 |
| Oceola | 292 |
| Octa | 58 |
| Ohio | 5,667 |
| Ohio City | 637 |
| Old Fort | 80 |
| Old Washington | 222 |
| Olde West Chester | 279 |
| Olive | 1,648 |
| Oliver | 1,329 |
| Olmsted | 14,280 |
| Olmsted Falls | 8,564 |
| Ontario | 6,650 |
| Orange | 3,518 |
| Orangeville | 168 |
| Oregon | 19,638 |
| Orient | 286 |
| Orrville | 8,409 |
| Orwell | 1,508 |
| Osgood | 296 |
| Osnaburg | 5,439 |
| Ostrander | 1,229 |
| Ottawa | 4,404 |
| Ottawa Hills | 4,781 |
| Ottoville | 970 |
| Otway | 89 |
| Owensville | 814 |
| Oxford | 22,104 |