| Merthyr Tudful to Oerlinghausen | 513.66 mi (826.66 km) |
| Merthyr Tudful to Oestrich-Winkel | 509.93 mi (820.66 km) |
| Merthyr Tudful to Offenburg | 549.24 mi (883.92 km) |
| Merthyr Tudful to Oftersheim | 549.36 mi (884.12 km) |
| Merthyr Tudful to Ohrdruf | 612.08 mi (985.04 km) |
| Merthyr Tudful to Ohringen | 592.03 mi (952.77 km) |
| Merthyr Tudful to Olbernhau | 725.62 mi (1,167.78 km) |
| Merthyr Tudful to Olching | 695.89 mi (1,119.93 km) |
| Merthyr Tudful to Oldenburg | 497.11 mi (800.03 km) |
| Merthyr Tudful to Oldenburg in Holstein | 617.25 mi (993.36 km) |
| Merthyr Tudful to Olfen | 460.11 mi (740.47 km) |
| Merthyr Tudful to Olpe | 485.60 mi (781.49 km) |
| Merthyr Tudful to Olsberg | 509.81 mi (820.46 km) |
| Merthyr Tudful to Oranienburg | 704.71 mi (1,134.12 km) |
| Merthyr Tudful to Ortenberg | 547.78 mi (881.57 km) |
