| Holyhead to Olivares | 1,100.45 mi (1,771.01 km) |
| Holyhead to Olivenza | 1,017.13 mi (1,636.91 km) |
| Holyhead to Olot | 835.97 mi (1,345.36 km) |
| Holyhead to Onate | 717.20 mi (1,154.22 km) |
| Holyhead to Onda | 944.71 mi (1,520.36 km) |
| Holyhead to Onteniente | 1,018.96 mi (1,639.86 km) |
| Holyhead to Orihuela | 1,066.40 mi (1,716.21 km) |
| Holyhead to Osuna | 1,110.95 mi (1,787.90 km) |
| Holyhead to Ourense | 772.59 mi (1,243.37 km) |
| Holyhead to Oviedo | 689.63 mi (1,109.86 km) |
| Holyhead to Paiporta | 979.48 mi (1,576.32 km) |
| Holyhead to Pajara | 1,790.51 mi (2,881.54 km) |
| Holyhead to Palafolls | 873.88 mi (1,406.37 km) |
| Holyhead to Palafrugell | 865.59 mi (1,393.03 km) |
| Holyhead to Palamos | 869.53 mi (1,399.37 km) |
