| Name | Meaning | Gender | Origin |
|---|
| Ody | | Unisex | |
| Oldman Sea Seashell | | Unisex | |
| Olivarez | | Unisex | |
| Olive | kind one; olive tree, peace. Symbol of peace. A small oval fruit. | Female | English |
| Oliver | The olive tree. The biblical olive tree symbolizes fruitfulness and beauty and dignity. Extending an olive branch signifies an offer of peace.
| Male | Latin |
| Omen | | Male | |
| One Direction | | Unisex | |
| Ontiveros | | Unisex | |
| Onyx | A gemstone with bands of different colours. | Male | |
| Onyxia | | Unisex | |
| Opal | Australian gemstone of remarkable colours, usually red, blue or green | Female | Sanskrit |
| Opal | Australian gemstone of remarkable colours, usually red, blue or green | Female | Sanskrit |
| Orca | | Unisex | |
| Orchid | | Female | |
| Ored | | Unisex | |
| Oreo | American cookie brand consisting of two chocolate wafers with white cream filling. | Male | |
| Oreo | American cookie brand consisting of two chocolate wafers with white cream filling. | Male | |
| Orion | Son of Fire
| Male | Greek |
| Osborne | soldier of God | Unisex | |
| Oswald Cobblepot | | Unisex | |
| Othello | he has the sound of God | Male | Hebrew |
| Othelo | | Unisex | |
| Pagan | from the country, countryman | Male | English |
| Pala | | Unisex | |
| Panda Bear | | Unisex | |