| Merthyr Tudful to Orbetello | 937.17 mi (1,508.23 km) |
| Merthyr Tudful to Oria | 1,263.43 mi (2,033.29 km) |
| Merthyr Tudful to Oristano | 997.74 mi (1,605.71 km) |
| Merthyr Tudful to Orta Nova | 1,151.90 mi (1,853.80 km) |
| Merthyr Tudful to Orte | 976.63 mi (1,571.73 km) |
| Merthyr Tudful to Ortona | 1,054.39 mi (1,696.87 km) |
| Merthyr Tudful to Orvieto | 954.05 mi (1,535.39 km) |
| Merthyr Tudful to Orzinuovi | 748.10 mi (1,203.95 km) |
| Merthyr Tudful to Osimo | 967.03 mi (1,556.28 km) |
| Merthyr Tudful to Ospitaletto | 746.35 mi (1,201.14 km) |
| Merthyr Tudful to Ostuni | 1,250.22 mi (2,012.04 km) |
| Merthyr Tudful to Ottaviano | 1,131.62 mi (1,821.16 km) |
| Merthyr Tudful to Ovada | 738.36 mi (1,188.27 km) |
| Merthyr Tudful to Ozieri | 969.52 mi (1,560.29 km) |
| Merthyr Tudful to Paceco | 1,224.21 mi (1,970.18 km) |
