World Sea Ports
| Port Name | Port Code | Country Name |
|---|---|---|
| Onne | NGONN | Nigeria |
| Onoaida | JPOAD | Japan |
| Onoda | JPOND | Japan |
| Onojo | JPNOJ | Japan |
| Onomichi | JPONO | Japan |
| OnomichiItozaki | JPONX | Japan |
| Onsan/Ulsan | KRONS | Korea, Republic of |
| Onslow | AUONS | Australia |
| Ontario | USOT5 | United States of America (the) |
| Ontonagon | USONG | United States of America (the) |