| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| Ormonde | - | English (Rare) | ||
| Orpha | AWR-fə (English) | Biblical, English | ||
| Orrell | - | English (Rare) | ||
| Orson | AWR-sən | English | ||
| Orval | AWR-vəl | English | ||
| Orville | AWR-vil | English | ||
| Osbert | AHZ-bərt | English (Rare) | ||
| Osborn | AHZ-born | English | ||
| Osborne | AHZ-born | English | ||
| Osbourne | AHZ-born | English (Rare) | ||
| Oscar | AHS-kər (English) | English, Irish, Portuguese (Brazilian), Italian, Swedish, Norwegian, Danish, Dutch, French, Irish My | ||
| Osmond | AHZ-mənd | English (Rare) | ||
| Oswald | AHZ-wawld (English), AWS-vahlt (German) | English, German, Anglo-Saxon | ||
| Oswin | AHZ-win | English (Rare) | ||
| Otis | O-tis | English |