| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| OcÉAne | o-se-AHN | French | ||
| Octave | - | French | ||
| Odette | o-DET | French | ||
| Odile | - | French | ||
| Odilon | - | French, Portuguese | ||
| Olivie | o-lee-VEE (French) | French, Czech | ||
| Olivier | o-lee-VYE (French), O-lee-veer (Dutch) | French, Dutch | ||
| Olympe | - | French | ||
| OnÉSime | - | French | ||
| Onfroi | - | Medieval French | ||
| OphÉLie | o-fe-LEE | French | ||
| Oriane | - | French | ||
| Orianne | - | French | ||
| Osanne | - | French (Rare) | ||
| Oscar | AHS-kər (English) | English, Irish, Portuguese (Brazilian), Italian, Swedish, Norwegian, Danish, Dutch, French, Irish My |