| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| Onisim | - | Russian (Rare) | ||
| Opaline | O-pə-leen | English (Rare) | ||
| Oral | - | English (Rare) | ||
| Oralee | - | English (Rare) | ||
| Oralie | - | English (Rare) | ||
| Orinda | - | English (Rare) | ||
| Ormond | AWR-mənd | English (Rare) | ||
| Ormonde | - | English (Rare) | ||
| Orrell | - | English (Rare) | ||
| Osanna | - | Italian (Rare) | ||
| Osanne | - | French (Rare) | ||
| Osbert | AHZ-bərt | English (Rare) | ||
| Osbourne | AHZ-born | English (Rare) | ||
| Osmond | AHZ-mənd | English (Rare) | ||
| Oswin | AHZ-win | English (Rare) |