| Obert | Man | French Names |
| Océane | Woman | French Names |
| Octave | Man | French Names |
| Odetta | Woman | French Names |
| Odette | Woman | French Names |
| Olivette | Woman | French Names |
| Olivier | Man | French Names |
| Olympe | Woman | French Names |
| Ondelette | Woman | French Names |
| Ondine | Woman | French Names |
| Opaque | Unisex | French Names |
| Ophélie | Woman | French Names |
| Orane | Unisex | French Names |
| Oriel | Unisex | French Names |
| Orleans | Unisex | French Names |
| Ottoline | Woman | French Names |
| Ouida | Woman | French Names |