| Onkel | - | Yiddish Name | Ono | - | Indonesian Name |
| Onphop | - | Thai Name | Onslow | - | Algerian Name |
| Onthawat | - | Thai Name | Onufrii | - | Ukrainian Name |
| Onufriy | - | Ukrainian Name | Onur | - | Turkish Name |
| Onuralp | - | Turkish Name | Onuris | - | Egyptian Name |
| Onya | - | Yiddish Name | Onyekachi | - | Cameroon Name |
| Onyrel | - | Cyprien Name | Onyx | - | United States Name |
| Oojam | - | Indian Name | Oojam | - | Hindu Name |
| Ookik | - | Eskimo Name | Oorjit | - | Indian Name |
| Oorjit | - | Hindu Name | Ootadabun | - | American Name |
| Ophir | - | Biblical Name | Ophni | - | Biblical Name |
| Ophrah | - | Biblical Name | Oppilmani | - | Indian Name |
| Oppilmani | - | Hindu Name | Orad | - | Aborigin Name |
| Oran | - | Irish Name | Oranil | - | Cyprien Name |
| Oranop | - | Thai Name | Oranuchai | - | Thai Name |
| Orbaal | - | Phoenician Name | Orçun | - | Turkish Name |
| Oreb | - | Biblical Name | Orel | - | Yiddish Name |
| Orelas | - | Cyprien Name | Oren | - | Aramaic Name |
| Orenthal | - | Hebrew Name | Orest | - | Ukrainian Name |
| Orest-Oleksandrovych | - | Ukrainian Name | Orestiv | - | Ukrainian Name |
| Orestko | - | Ukrainian Name | Orhan | - | Turkish Name |
| Ori | - | Indian Name | Ori | - | Hindu Name |
| Ori | - | Polynesian Name |
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