| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| OlÍVia | - | Portuguese, Slovak, Hungarian | ||
| Olga | OL-gah (Russian), AWL-gah (Polish, German) | Russian, Ukrainian, Polish, German, Swedish, Norwegian, Danish, Icelandic, Latvian, Hungarian, Itali | ||
| Olimpia | aw-LEEM-pyah (Polish) | Italian, Spanish, Romanian, Polish, Hungarian | ||
| OlivÉR | O-lee-vayr | Hungarian | ||
| OrbÁN | - | Hungarian | ||
| Orsolya | - | Hungarian | ||
| OszkÁR | - | Hungarian | ||
| OttÓ | - | Hungarian, Icelandic |