| Onofledis | Shows her Sword |
| Onoria | A name meaning one of honor. |
| Onorine | A name meaning honorable or noble. |
| Onsiyah | A name meaning a peaceful companion. |
| Ontario | Beautiful place, a Native American name meaning lovely location |
| Onu | A name meaning a leader or a chief. |
| Onukka | A name meaning a gift from the gods. |
| Onya | A name meaning a graceful mountain. |
| Onyka | God is my joy, a Nigerian name meaning divine happiness |
| Ooma | A name meaning a source of wisdom. |
| Oorvasi | To Rise, The Ganges |
| Oota dabun | Gift of the forest, a Native American name meaning woodland treasure |
| Opis | Goddess of Fertility |
| Oportuna | A name meaning timely or lucky. |
| Optimus | Best, a Latin name meaning superior or excellent |
| Opus | Work, a Latin name meaning creation or achievement |
| Orabilia | A name meaning easy to pray to. |
| Orabilis | A name meaning worthy of prayer. |
| Orable | A name meaning golden and bright. |
| Oraiba | Keen, Discerning, Intelligent |
| Oralit | A name meaning golden light. |
| Orania | Derived from the golden sun. |
| Orawin | A friend of golden light. |
| Orazia | One who brings golden joy. |
| Ordmaer | A noble and golden ruler. |
| Oreekha | Affectionate Personality |
| Orelee | Meaning a golden meadow path. |
| Orelon | A strong golden mountain. |
| Orena | Meaning a golden peace lily. |
| Orenge | A vibrant golden fruit tree. |
| Orengia | A beautiful golden flower. |
| Orestia | Mountain Goddess |
| Oreta | Woman of Virtue |
| Oretta | Woman of Virtue |
| Orette | Woman of Virtue |
| Oreute | A name meaning mountain dweller. |
| Orev | God is my shepherd, a Hebrew name meaning divine guidance |
| Orfhlaith | A golden princess of the realm. |
| Orfilia | One who is a golden leaf of life. |
| Organa | A name meaning musical instrument. |