| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| Ottmar | - | German | ||
| Otto | AW-to (German), AH-to (English), OT-to (Finnish) | German, Swedish, Norwegian, Danish, Dutch, English, Finnish, Ancient Germanic | ||
| Ottokar | - | German | ||
| Ottomar | - | German | ||
| Ottone | - | Italian | ||
| Ottorino | - | Italian | ||
| Ove | - | Swedish, Norwegian, Danish | ||
| Ovidio | - | Italian, Spanish | ||
| Ovidiu | - | Romanian | ||
| Ovidius | - | Ancient Roman | ||
| Owain | O-wien (Welsh, Welsh Mythology) | Welsh, Welsh Mythology, Arthurian Romance | ||
| Oxana | - | Ukrainian, Russian | ||
| Oyibo | - | Western African, Urhobo | ||
| Oyunchimeg | - | Mongolian |