| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| ONISIMU | - | Old Church Slavic | ||
| ONNI | ON-nee | Finnish | ||
| ONUR | - | Turkish | ||
| ONYEKA | - | Western African, Igbo | ||
| ONYEKACHI | - | Western African, Igbo | ||
| ONYEKACHUKWU | - | Western African, Igbo | ||
| OONA | OO-na (Irish), O:-nah (Finnish) | Irish, Finnish | ||
| OONAGH | OO-na | Irish | ||
| Opal | ['əupəl] | |||
| OPAL | O-pəl | English | ||
| OPALINE | O-pə-leen | English (Rare) | ||
| OPEYEMI | - | Western African, Yoruba | ||
| OPHÉLIE | o-fe-LEE | French | ||
| Ophelia | [əu'fi:liə] | |||
| OPHELIA | o-FEEL-yə (English) | English, Literature |