| Oafe | Woman | African - Ishan of Nigeria Names |
| Oakes | Unisex | English Names |
| Oakley | Unisex | English Names |
| Oaklynn | Woman | American Names |
| Oba | Man | African - Nigeria Names |
| Obadiah | Man | Hebrew Names |
| Obama | Unisex | African - Luo of Kenyan Names |
| Obedience | Woman | English Names |
| Obelia | Woman | Greek Names |
| Oberon | Unisex | German Names |
| Obert | Man | French Names |
| Obioma | Woman | African - Nigeria Names |
| Oburu | Man | African - Luo of Kenya Names |
| Occhave | Man | Indian Names |
| Ocean | Unisex | Greek Names |
| Oceana | Woman | Greek Names |
| Océane | Woman | French Names |
| Oceanus | Man | Latin Names |
| Ocheckka | Unisex | Native American - Winnebago Names |
| Ochoa | Unisex | Spanish Names |