| Holyhead to Oerlinghausen | 564.45 mi (908.39 km) |
| Holyhead to Oestrich-Winkel | 586.78 mi (944.34 km) |
| Holyhead to Offenburg | 640.49 mi (1,030.77 km) |
| Holyhead to Oftersheim | 630.81 mi (1,015.19 km) |
| Holyhead to Ohrdruf | 673.29 mi (1,083.56 km) |
| Holyhead to Ohringen | 672.35 mi (1,082.04 km) |
| Holyhead to Olbernhau | 783.67 mi (1,261.20 km) |
| Holyhead to Olching | 779.12 mi (1,253.87 km) |
| Holyhead to Oldenburg | 530.79 mi (854.23 km) |
| Holyhead to Oldenburg in Holstein | 635.49 mi (1,022.72 km) |
| Holyhead to Olfen | 516.45 mi (831.14 km) |
| Holyhead to Olpe | 550.76 mi (886.37 km) |
| Holyhead to Olsberg | 569.23 mi (916.09 km) |
| Holyhead to Oranienburg | 741.56 mi (1,193.42 km) |
| Holyhead to Ortenberg | 617.88 mi (994.38 km) |
