World Sea Ports
| Port Name | Port Code | Country Name |
|---|---|---|
| Omø | DKOMO | Denmark |
| Omu | JPOUM | Japan |
| Omura | JPOMJ | Japan |
| Omuta | JPOMU | Japan |
| Ön | SEOEN | Sweden |
| Onagawa | JPONG | Japan |
| Onahama | JPONA | Japan |
| Onawa | USIA3 | United States of America (the) |
| Ondárroa | ESOND | Spain |
| Ondes | FRJFM | France |