| Name | What | Region | Country | Lat | Long | Elev ft. | Pop est |
|---|---|---|---|---|---|---|---|
| Оксилитос | city | Sterea Ellada | Greece | 38.58 | 24.11 | 396 | 3976 |
| Октония | city | Sterea Ellada | Greece | 38.53 | 24.16 | 1725 | 2549 |
| Олинт | city | Kentriki Makedonia | Greece | 40.29 | 23.34 | 36 | 7732 |
| Олинф | city | Kentriki Makedonia | Greece | 40.29 | 23.34 | 36 | 7732 |
| Олишча | city | Dytiki Makedonia | Greece | 40.58 | 21.40 | 2509 | 1075 |
| Олища | city | Dytiki Makedonia | Greece | 40.58 | 21.40 | 2509 | 1075 |
| Олінфос | city | Kentriki Makedonia | Greece | 40.29 | 23.34 | 36 | 7732 |
| Омур бей | city | Kentriki Makedonia | Greece | 40.85 | 23.68 | 830 | 1436 |
| Ореи | city | Sterea Ellada | Greece | 38.95 | 23.09 | 124 | 4842 |
| Орестиада | city | Anatoliki Makedonia kai Thraki | Greece | 41.51 | 26.53 | 72 | 11967 |
| Орио | city | Sterea Ellada | Greece | 38.53 | 24.12 | 150 | 3463 |
| Орманъ | city | Dytiki Makedonia | Greece | 40.52 | 21.21 | 2509 | 12323 |
| Ормилия | city | Kentriki Makedonia | Greece | 40.29 | 23.54 | 55 | 3745 |
| Ормос Принос | city | Anatoliki Makedonia kai Thraki | Greece | 40.76 | 24.58 | 19 | 1557 |
| Орологио | city | Sterea Ellada | Greece | 38.53 | 24.09 | 318 | 3458 |
| Оропос | city | Attiki | Greece | 38.30 | 23.75 | 341 | 10467 |
| Ортониес | city | Ionia Nisia | Greece | 37.85 | 20.69 | 1669 | 2290 |
| Орхомен | city | Sterea Ellada | Greece | 38.49 | 22.98 | 328 | 8029 |
| Орѣховица | city | Kentriki Makedonia | Greece | 41.04 | 22.58 | 830 | 3323 |
| Осеница | city | Anatoliki Makedonia kai Thraki | Greece | 41.37 | 24.24 | 1925 | 947 |
| Осничани | city | Dytiki Makedonia | Greece | 40.36 | 21.16 | 3425 | 1940 |