| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| Ognen | - | Macedonian | ||
| Ognena | - | Macedonian | ||
| Ognjan | - | Croatian, Serbian | ||
| Ognjen | - | Croatian, Serbian | ||
| Ohad | - | Biblical | ||
| Oighrig | - | Scottish | ||
| Okoro | - | Western African, Urhobo | ||
| Olabode | - | Western African, Yoruba | ||
| Olaf | O-lahf (German, Dutch) | Norwegian, Danish, German, Dutch, Polish | ||
| Olamide | - | Western African, Yoruba | ||
| Olamilekan | - | Western African, Yoruba | ||
| Olanrewaju | - | Western African, Yoruba | ||
| Olayinka | - | Western African, Yoruba | ||
| OldŘIch | - | Czech | ||
| Olga | OL-gah (Russian), AWL-gah (Polish, German) | Russian, Ukrainian, Polish, German, Swedish, Norwegian, Danish, Icelandic, Latvian, Hungarian, Itali |