| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| Origenes | - | Ancient Greek | ||
| Ortwin | AWRT-veen (German) | German, Ancient Germanic | ||
| Othmar | - | German, Czech, Ancient Germanic | ||
| Otmar | - | German, Ancient Germanic | ||
| Otto | AW-to (German), AH-to (English), OT-to (Finnish) | German, Swedish, Norwegian, Danish, Dutch, English, Finnish, Ancient Germanic | ||
| Pamphilos | - | Ancient Greek | ||
| Pancratius | - | Ancient Greek (Latinized) | ||
| Pankratios | - | Ancient Greek | ||
| Pantaleon | - | Ancient Greek | ||
| Panther | - | Ancient Greek | ||
| Pantheras | - | Ancient Greek | ||
| Paramonos | - | Ancient Greek | ||
| Pelagia | pe-LAHG-yah (Polish) | Ancient Greek, Greek, Polish | ||
| Pelagios | - | Ancient Greek | ||
| Pelagius | - | Ancient Greek (Latinized) |