| Olanrewaju | | - | Western African, Yoruba | |
| Olayinka | | - | Western African, Yoruba | |
| OldŘIch | | - | Czech | |
| Olga | | OL-gah (Russian), AWL-gah (Polish, German) | Russian, Ukrainian, Polish, German, Swedish, Norwegian, Danish, Icelandic, Latvian, Hungarian, Itali | |
| Olgica | | - | Macedonian, Serbian | |
| Oliver | | AHL-ə-vər (English), AW-lee-ver (German), O-lee-ver (Finnish) | English, German, Swedish, Norwegian, Danish, Finnish, Estonian, Serbian, Croatian, Macedonian, Czech | |
| Olivera | | - | Serbian, Croatian, Macedonian | |
| Olivie | | o-lee-VEE (French) | French, Czech | |
| Olivier | | o-lee-VYE (French), O-lee-veer (Dutch) | French, Dutch | |
| Olubunmi | | - | Western African, Yoruba | |
| Oluchi | | - | Western African, Igbo | |
| Olufemi | | - | Western African, Yoruba | |
| Olufunke | | - | Western African, Yoruba | |
| Olufunmilayo | | o-loo-foo-mee-LIE-o | Western African, Yoruba | |
| Olufunmilola | | - | Western African, Yoruba | |