| Otmar | | - | German, Ancient Germanic | |
| Otto | | AW-to (German), AH-to (English), OT-to (Finnish) | German, Swedish, Norwegian, Danish, Dutch, English, Finnish, Ancient Germanic | |
| Ovidius | | - | Ancient Roman | |
| Pamphilos | | - | Ancient Greek | |
| Pancratius | | - | Ancient Greek (Latinized) | |
| Pankratios | | - | Ancient Greek | |
| Pantaleon | | - | Ancient Greek | |
| Panther | | - | Ancient Greek | |
| Pantheras | | - | Ancient Greek | |
| Papak | | - | Ancient Persian | |
| Paramonos | | - | Ancient Greek | |
| Paulina | | pow-LEE-nah (Spanish, Polish), paw-LEEN-ə (English) | Spanish, Portuguese, Polish, Swedish, Lithuanian, English, Ancient Roman | |
| Paulinus | | - | Ancient Roman | |
| Paulus | | - | Ancient Roman, Biblical Latin | |
| Pelagia | | pe-LAHG-yah (Polish) | Ancient Greek, Greek, Polish | |