| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| Oli | AHL-ee | English | ||
| Olive | AHL-iv | English | ||
| Oliver | AHL-ə-vər (English), AW-lee-ver (German), O-lee-ver (Finnish) | English, German, Swedish, Norwegian, Danish, Finnish, Estonian, Serbian, Croatian, Macedonian, Czech | ||
| Olivia | ə-LIV-ee-ə (English), o-LEE-vyah (Italian, Spanish), o-LEE-vee-ah (German), O-lee-vee-ah (Finnish) | English, Italian, Spanish, German, Finnish, Swedish, Norwegian, Danish | ||
| Ollie | AHL-ee | English | ||
| Olyvia | ə-LIV-ee-ə | English (Rare) | ||
| Omar (1) | - | Arabic, English | ||
| Oneida | o-NIE-də | English | ||
| Opal | O-pəl | English | ||
| Opaline | O-pə-leen | English (Rare) | ||
| Ophelia | o-FEEL-yə (English) | English, Literature | ||
| Ora (1) | - | English | ||
| Oral | - | English (Rare) | ||
| Oralee | - | English (Rare) | ||
| Oralie | - | English (Rare) |