| City | Region |
|---|
| ›Ochiro | Evros› |
| ›Olena (Oleni) | Ileia› |
| ›Olenia | Achaia› |
| ›Omala | Kefallinia› |
| ›Onia | Dodekanisos (Kos Island)› |
| ›Oreoi | Evvoia› |
| ›Orestias (Orestiada) | Evros› |
| ›Orfeas | Evros› |
| ›Ormenio | Evros› |
| ›Ormos Agiou Isidorou | Voreío Aigaío› |
| ›Ormos Athinios | Kyklades (Thira Island)› |
