| Merthyr Tudful to Mangualde | 797.30 mi (1,283.13 km) |
| Merthyr Tudful to Marco de Canavezes | 763.71 mi (1,229.07 km) |
| Merthyr Tudful to Marinha Grande | 870.21 mi (1,400.46 km) |
| Merthyr Tudful to Massama | 941.21 mi (1,514.74 km) |
| Merthyr Tudful to Matosinhos | 771.79 mi (1,242.08 km) |
| Merthyr Tudful to Mealhada | 821.17 mi (1,321.55 km) |
| Merthyr Tudful to Melgaco | 703.57 mi (1,132.28 km) |
| Merthyr Tudful to Melres | 775.02 mi (1,247.28 km) |
| Merthyr Tudful to Mira | 821.92 mi (1,322.75 km) |
| Merthyr Tudful to Miranda do Corvo | 838.47 mi (1,349.39 km) |
| Merthyr Tudful to Mirandela | 731.10 mi (1,176.60 km) |
| Merthyr Tudful to Mogadouro | 736.33 mi (1,185.01 km) |
| Merthyr Tudful to Moimenta da Beira | 770.27 mi (1,239.62 km) |
| Merthyr Tudful to Moita | 944.20 mi (1,519.54 km) |
| Merthyr Tudful to Moncao | 709.75 mi (1,142.23 km) |
