| Merthyr Tudful to Monticello (Minnesota) | 3,889.52 mi (6,259.58 km) |
| Merthyr Tudful to Montrose (Colorado) | 4,729.65 mi (7,611.63 km) |
| Merthyr Tudful to Moody (Alabama) | 4,162.37 mi (6,698.69 km) |
| Merthyr Tudful to Moore (Oklahoma) | 4,511.27 mi (7,260.18 km) |
| Merthyr Tudful to Moorestown-Lenola (New Jersey) | 3,394.85 mi (5,463.48 km) |
| Merthyr Tudful to Mooresville (North Carolina) | 3,834.86 mi (6,171.62 km) |
| Merthyr Tudful to Moorhead (Minnesota) | 3,921.60 mi (6,311.20 km) |
| Merthyr Tudful to Moorpark (California) | 5,331.73 mi (8,580.59 km) |
| Merthyr Tudful to Moraga (California) | 5,231.95 mi (8,420.02 km) |
| Merthyr Tudful to Moreno Valley (California) | 5,296.86 mi (8,524.47 km) |
| Merthyr Tudful to Morgan City (Louisiana) | 4,547.66 mi (7,318.76 km) |
| Merthyr Tudful to Morgan Hill (California) | 5,257.86 mi (8,461.71 km) |
| Merthyr Tudful to Morganton (North Carolina) | 3,863.46 mi (6,217.63 km) |
| Merthyr Tudful to Morgantown (West Virginia) | 3,612.73 mi (5,814.13 km) |
| Merthyr Tudful to Morris (Illinois) | 3,869.65 mi (6,227.60 km) |
