| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| Oswald | AHZ-wawld (English), AWS-vahlt (German) | English, German, Anglo-Saxon | ||
| Oswin | AHZ-win | English (Rare) | ||
| Oswine | - | Anglo-Saxon | ||
| OtÁVia | - | Portuguese (Brazilian) | ||
| OtÁVio | - | Portuguese (Brazilian) | ||
| Otieno | - | Eastern African, Luo | ||
| Otis | O-tis | English | ||
| Otso | OT-so | Finnish | ||
| Ottilia | oot-TEE-lee-ah | Swedish | ||
| Otto | AW-to (German), AH-to (English), OT-to (Finnish) | German, Swedish, Norwegian, Danish, Dutch, English, Finnish, Ancient Germanic | ||
| Ottoline | - | English (Rare) | ||
| Otylia | - | Polish | ||
| Ouida | - | Various | ||
| OvÍDio | - | Portuguese | ||
| Ove | - | Swedish, Norwegian, Danish |