World Sea Ports
| Port Name | Port Code | Country Name |
|---|---|---|
| Oldendorf | DEOLD | Germany |
| Olderdalen | NOOLL | Norway |
| Oldersum | DEOLU | Germany |
| Oldervik | NOOLR | Norway |
| Oldham | GBODH | United Kingdom |
| Olee Lheue | IDOLO | Indonesia |
| Olekminsk | RUOMK | Russian Federation (the) |
| Olen | BEOLN | Belgium |
| Oleniy Ostrov | RUOLO | Russian Federation (the) |
| Olenya, Guba | RUOLG | Russian Federation (the) |