| Obelia | Woman | Greek Names |
| Ocean | Unisex | Greek Names |
| Oceana | Woman | Greek Names |
| Odessa | Woman | Greek Names |
| Odysseus | Man | Greek Names |
| Oleander | Man | Greek Names |
| Olympia | Woman | Greek Names |
| Omega | Unisex | Greek Names |
| Omiros | Man | Greek Names |
| Onofrio | Man | Greek Names |
| Ophelia | Woman | Greek Names |
| Oracle | Unisex | Greek Names |
| Orestes | Man | Greek Names |
| Orianthe | Woman | Greek Names |
| Orion | Unisex | Greek Names |
| Orpheus | Man | Greek Names |
| Osanna | Woman | Greek Names |
| Osiris | Man | Greek Names |
| Ourania | Woman | Greek Names |