| Merthyr Tudful to Opwijk | 330.48 mi (531.86 km) |
| Merthyr Tudful to Ostend | 273.21 mi (439.69 km) |
| Merthyr Tudful to Oud-Heverlee | 353.07 mi (568.21 km) |
| Merthyr Tudful to Oud-Turnhout | 360.40 mi (580.01 km) |
| Merthyr Tudful to Oudenaarde | 307.59 mi (495.02 km) |
| Merthyr Tudful to Oudenburg | 277.17 mi (446.06 km) |
| Merthyr Tudful to Oupeye | 396.57 mi (638.21 km) |
| Merthyr Tudful to Overijse | 348.23 mi (560.42 km) |
| Merthyr Tudful to Overpelt | 379.95 mi (611.47 km) |
| Merthyr Tudful to Paal | 371.63 mi (598.09 km) |
| Merthyr Tudful to Peer | 382.47 mi (615.52 km) |
| Merthyr Tudful to Pepinster | 406.38 mi (654.00 km) |
| Merthyr Tudful to Peruwelz | 313.37 mi (504.32 km) |
| Merthyr Tudful to Perwez | 362.95 mi (584.11 km) |
| Merthyr Tudful to Philippeville | 360.82 mi (580.69 km) |
