| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| OldŘIch | - | Czech | ||
| Oliver | AHL-ə-vər (English), AW-lee-ver (German), O-lee-ver (Finnish) | English, German, Swedish, Norwegian, Danish, Finnish, Estonian, Serbian, Croatian, Macedonian, Czech | ||
| Olivie | o-lee-VEE (French) | French, Czech | ||
| OndŘEj | - | Czech | ||
| Otakar | - | Czech | ||
| Othmar | - | German, Czech, Ancient Germanic | ||
| Otokar | - | Czech |