| Merthyr Tudful to Nuth | 403.60 mi (649.53 km) |
| Merthyr Tudful to Oegstgeest | 335.19 mi (539.44 km) |
| Merthyr Tudful to Oirschot | 372.42 mi (599.35 km) |
| Merthyr Tudful to Oisterwijk | 367.58 mi (591.57 km) |
| Merthyr Tudful to Oldebroek | 396.55 mi (638.19 km) |
| Merthyr Tudful to Oldenzaal | 439.74 mi (707.70 km) |
| Merthyr Tudful to Ommen | 418.53 mi (673.56 km) |
| Merthyr Tudful to Oosterend | 407.47 mi (655.77 km) |
| Merthyr Tudful to Oosterhout | 352.57 mi (567.41 km) |
| Merthyr Tudful to Oosterwolde | 416.60 mi (670.45 km) |
| Merthyr Tudful to Oostzaan | 353.76 mi (569.31 km) |
| Merthyr Tudful to Opmeer | 358.43 mi (576.85 km) |
| Merthyr Tudful to Oss | 380.20 mi (611.87 km) |
| Merthyr Tudful to Oud-Beijerland | 332.37 mi (534.89 km) |
| Merthyr Tudful to Oudenbosch | 338.63 mi (544.98 km) |
