| Orsin | Man | English Names |
| Orsina | Woman | Italian Names |
| Orsino | Man | Italian Names |
| Orson | Man | English Names |
| Ortega | Unisex | Spanish Names |
| Ortiz | Man | Spanish Names |
| Orville | Man | English Names |
| Orwa | Man | African - Luo of Kenya Names |
| Orya | Woman | Russian Names |
| Osama | Man | Arabic Names |
| Osamu | Man | Japanese Names |
| Osanna | Woman | Greek Names |
| Osbert | Man | English Names |
| Osborn | Man | English Names |
| Osbourne | Man | English Names |
| Oscar | Man | Irish Names |
| Osceola | Unisex | Native American - Seminole Names |
| Oscosh | Man | Native American - Menominee Names |
| Osgood | Man | English Names |
| Osgyth | Woman | English - Old English Names |