| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| Odilia | - | Ancient Germanic | ||
| Odilo | - | Ancient Germanic | ||
| Odo | - | Ancient Germanic | ||
| Odoacer | o-do-AY-sər (English) | Ancient Germanic | ||
| Odovacar | o-do-VAY-kər (English) | Ancient Germanic | ||
| Olympias | - | Ancient Greek | ||
| Olympiodoros | - | Ancient Greek | ||
| Olympos | - | Ancient Greek | ||
| Onesimos | - | Ancient Greek, Biblical Greek | ||
| Onesiphoros | - | Ancient Greek, Biblical Greek | ||
| Origenes | - | Ancient Greek | ||
| Ortwin | AWRT-veen (German) | German, Ancient Germanic | ||
| Othmar | - | German, Czech, Ancient Germanic | ||
| Otho | - | Ancient Roman | ||
| Otmar | - | German, Ancient Germanic |