| Merthyr Tudful to Oberkirch | 553.11 mi (890.15 km) |
| Merthyr Tudful to Obernburg am Main | 561.62 mi (903.85 km) |
| Merthyr Tudful to Obernkirchen | 532.06 mi (856.26 km) |
| Merthyr Tudful to Oberschleissheim | 704.74 mi (1,134.17 km) |
| Merthyr Tudful to Oberstdorf | 679.77 mi (1,093.99 km) |
| Merthyr Tudful to Obertraubling | 710.09 mi (1,142.78 km) |
| Merthyr Tudful to Obertshausen | 543.82 mi (875.20 km) |
| Merthyr Tudful to Oberursel | 530.25 mi (853.35 km) |
| Merthyr Tudful to Ochsenfurt | 604.97 mi (973.60 km) |
| Merthyr Tudful to Ochsenhausen | 643.73 mi (1,035.99 km) |
| Merthyr Tudful to Ochtrup | 450.55 mi (725.08 km) |
| Merthyr Tudful to Odenthal | 454.75 mi (731.85 km) |
| Merthyr Tudful to Oelde | 492.22 mi (792.15 km) |
| Merthyr Tudful to Oelsnitz | 679.61 mi (1,093.73 km) |
| Merthyr Tudful to Oer-Erkenschwick | 454.88 mi (732.05 km) |
