| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| Obi | - | Western African, Igbo | ||
| OctÁVia | - | Portuguese | ||
| OctÁVio | - | Portuguese | ||
| Odilon | - | French, Portuguese | ||
| OfÉLia | - | Portuguese | ||
| Ogechi | - | Western African, Igbo | ||
| Ogechukwukama | - | Western African, Igbo | ||
| Oghenekaro | - | Western African, Urhobo | ||
| Oghenekevwe | - | Western African, Urhobo | ||
| Oghenero | - | Western African, Urhobo | ||
| Okoro | - | Western African, Urhobo | ||
| OlÍVia | - | Portuguese, Slovak, Hungarian | ||
| Olabode | - | Western African, Yoruba | ||
| Olamide | - | Western African, Yoruba | ||
| Olamilekan | - | Western African, Yoruba |