| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| Ofelia | o-FE-lyah | Spanish, Italian | ||
| Olalla | o-LAH-yah | Spanish | ||
| Olegario | - | Spanish | ||
| Olimpia | aw-LEEM-pyah (Polish) | Italian, Spanish, Romanian, Polish, Hungarian | ||
| 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 | ||
| Orfeo | - | Italian, Spanish | ||
| Osvaldo | - | Spanish, Italian, Portuguese | ||
| Ovidio | - | Italian, Spanish | ||
| PÁNfilo | - | Spanish | ||
| PÍA | PEE-ah | Spanish | ||
| PÍO | PEE-o | Spanish | ||
| Pablo | PAH-blo | Spanish | ||
| PacÍFica | pah-THEE-fee-kah (Spanish), pah-SEE-fee-kah (Latin American Spanish) | Spanish | ||
| Paca | PAH-kah | Spanish | ||
| Paco | PAH-ko | Spanish |