| Holyhead to Oberkirch | 643.35 mi (1,035.38 km) |
| Holyhead to Obernburg am Main | 636.91 mi (1,025.01 km) |
| Holyhead to Obernkirchen | 578.16 mi (930.47 km) |
| Holyhead to Oberschleissheim | 786.94 mi (1,266.46 km) |
| Holyhead to Oberstdorf | 771.18 mi (1,241.09 km) |
| Holyhead to Obertraubling | 785.35 mi (1,263.90 km) |
| Holyhead to Obertshausen | 617.61 mi (993.95 km) |
| Holyhead to Oberursel | 603.26 mi (970.85 km) |
| Holyhead to Ochsenfurt | 679.63 mi (1,093.76 km) |
| Holyhead to Ochsenhausen | 731.70 mi (1,177.56 km) |
| Holyhead to Ochtrup | 499.64 mi (804.09 km) |
| Holyhead to Odenthal | 521.43 mi (839.16 km) |
| Holyhead to Oelde | 545.62 mi (878.09 km) |
| Holyhead to Oelsnitz | 742.19 mi (1,194.43 km) |
| Holyhead to Oer-Erkenschwick | 512.56 mi (824.88 km) |
