| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| OIGHRIG | - | Scottish | ||
| OIHANA | - | Basque | ||
| OILI | OY-lee | Finnish | ||
| OINONE | - | Greek Mythology | ||
| OISÍN | OSH-een, USH-een | Irish, Irish Mythology | ||
| OIVA | OY-vah | Finnish | ||
| OKEANOS | - | Greek Mythology | ||
| OKORO | - | Western African, Urhobo | ||
| OKROPIR | - | Georgian | ||
| OKSANA | ahk-SAH-nah (Russian) | Ukrainian, Russian | ||
| OLÍVIA | - | Portuguese, Slovak, Hungarian | ||
| OLA (1) | - | Norwegian, Swedish | ||
| OLA (2) | AW-lah | Polish | ||
| OLABODE | - | Western African, Yoruba | ||
| OLAF | O-lahf (German, Dutch) | Norwegian, Danish, German, Dutch, Polish |