World Sea Ports
| Port Name | Port Code | Country Name |
|---|---|---|
| Olazagutía | ESOLZ | Spain |
| Olbia | ITOLB | Italy |
| Old Brookville | USDXX | United States of America (the) |
| Old Dalby | GBODL | United Kingdom |
| Old Dornie | GBODO | United Kingdom |
| Old Kilpatrick | GBOKK | United Kingdom |
| Old Rock Hill | USDKH | United States of America (the) |
| Olden | NOOLD | Norway |
| Oldenburg | DEOLO | Germany |
| Oldenbüttel | DEOLB | Germany |