| Osuuald | Derived from Old English, means 'divine power' or 'power of God' |
| Osuualdus | Old English name meaning 'divine power' or 'power of God' |
| Osuuol | Derived from Old English, means 'divine wolf' or 'wolf of God' |
| Osuuold | Old English name meaning 'divine power' or 'power of God' |
| Osuuoldus | Derived from Old English, means 'divine power' or 'power of God' |
| Oswall | Rule of God; Divine Power |
| Oswinus | Latin origin, meaning 'divine friend' or 'friend of God' |
| Oswold | Rule of God; Divine Power |
| Oswudu | Old English, meaning 'divine wood' or 'wood of God' |
| Oswuff | Old English, possibly meaning 'divine wolf' or 'wolf of God' |
| Oswulf | Means divine wolf in English. |
| Osyth | Old English, meaning 'divine strength' or 'strong in God' |
| Otta | Means wealthy or prosperous. |
| Ottewell | Old English, meaning 'brave well' or 'strong well' |
| Otuel | Old English, meaning 'brave people' or 'strong tribe' |
| Oudoceus | Latin origin, meaning 'good news' or 'joyful tidings' |
| Ouein | Greek origin, meaning 'good' or 'beautiful' |
| Oughtred | Old English, meaning 'brave counsel' or 'strong advice' |
| Owaine | Youth; Lamb; Yahweh is Gracious |
| Oxforde | Place name origin, meaning 'ox ford' or 'ford of oxen' |
| Ozwell | Old English, possibly meaning 'divine well' or 'well of God' |
| Osher | One who brings joy and happiness. |
| Ozer | A person who provides assistance. |
| Oakki | A name meaning strong like an oak. |
| Oatam | A name meaning a gift of the earth. |
| Oatikki | A name meaning a small forest dweller. |
| Ohvana | A name meaning a peaceful spirit. |
| Oikka | Splendid; Excellent |
| Oikki | Splendid; Excellent |
| Oikku | Splendid; Excellent |
| Oippo | Splendid; Excellent |
| Oiva | Excellent; Splendid |
| Okke | Wealth; Fortune |
| Okki | God Spear; Gentle Friend |
| Okko | Wealth; Fortune |
| Oku | A name meaning a deep inner wisdom. |
| Oleks | Defending Men; Warrior |
| Oleksei | Defending Men; Warrior |
| Oleksi | Defending Men; Warrior |
| Olesa | Defender of Men |