| Ochoa | Unisex | Spanish Names |
| Odalys | Unisex | Spanish Names |
| Oderico | Man | Spanish Names |
| Odón | Man | Spanish Names |
| Olalla | Man | Spanish Names |
| Oliana | Woman | Spanish Names |
| Olimpio | Man | Spanish Names |
| Ondina | Woman | Spanish Names |
| Onelia | Woman | Spanish Names |
| Onelio | Man | Spanish Names |
| Onofre | Man | Spanish Names |
| Ora | Woman | Spanish Names |
| Oracion | Unisex | Spanish Names |
| Oro | Man | Spanish Names |
| Orozco | Unisex | Spanish Names |
| Orquidea | Woman | Spanish Names |
| Ortega | Unisex | Spanish Names |
| Ortiz | Man | Spanish Names |
| Osmundo | Man | Spanish Names |
| Osvaldo | Man | Spanish Names |