| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| Otto | AW-to (German), AH-to (English), OT-to (Finnish) | German, Swedish, Norwegian, Danish, Dutch, English, Finnish, Ancient Germanic | ||
| Ottokar | - | German | ||
| Ottoline | - | English (Rare) | ||
| Ottomar | - | German | ||
| Ottone | - | Italian | ||
| Ottorino | - | Italian | ||
| Ouida | - | Various | ||
| Ourbanos | - | Biblical Greek | ||
| Ouri | - | Biblical Greek | ||
| Ourias | - | Biblical Greek | ||
| Ove | - | Swedish, Norwegian, Danish | ||
| Oved | - | Hebrew, Biblical Hebrew | ||
| Ovidio | - | Italian, Spanish | ||
| Ovidiu | - | Romanian | ||
| Ovidius | - | Ancient Roman |