The Area Codes of Ukraine:
| City/Town or Region | Area code | |
|---|---|---|
| 1. | Obukhiv | 4572 (+380 4572) |
| 2. | Ochakiv | 5154 (+380 5154) |
| 3. | Odessa | 48 (+380 48) |
| 4. | Okhtyrka | 5446 (+380 5446) |
| 5. | Okny | 4861 (+380 4861) |
| 6. | Oleksandrivka | 5242 (+380 5242) |
| 7. | Oleksandrivka | 6269 (+380 6269) |
| 8. | Oleksandrivsk | 642 (+380 642) |
| 9. | Oleksandriya | 5235 (+380 5235) |
| 10. | Olevsk | 4135 (+380 4135) |
| 11. | Onufriyivka | 5238 (+380 5238) |
| 12. | Orativ | 4330 (+380 4330) |
| 13. | Ordzhonikidze | 5667 (+380 5667) |
| 14. | Orikhiv | 6141 (+380 6141) |
| 15. | Orzhytsia | 5357 (+380 5357) |
| 16. | Ostroh | 3654 (+380 3654) |
| 17. | Ovidiopol | 4851 (+380 4851) |
| 18. | Ovruch | 4148 (+380 4148) |