| Middle River to Mangualde | 3,539.47 mi (5,696.22 km) |
| Middle River to Marco de Canavezes | 3,505.55 mi (5,641.64 km) |
| Middle River to Marinha Grande | 3,504.97 mi (5,640.71 km) |
| Middle River to Massama | 3,514.91 mi (5,656.71 km) |
| Middle River to Matosinhos | 3,478.99 mi (5,598.89 km) |
| Middle River to Mealhada | 3,511.83 mi (5,651.74 km) |
| Middle River to Melgaco | 3,476.30 mi (5,594.56 km) |
| Middle River to Melres | 3,496.48 mi (5,627.04 km) |
| Middle River to Mira | 3,496.73 mi (5,627.44 km) |
| Middle River to Miranda do Corvo | 3,525.01 mi (5,672.95 km) |
| Middle River to Mirandela | 3,544.32 mi (5,704.03 km) |
| Middle River to Mogadouro | 3,570.60 mi (5,746.32 km) |
| Middle River to Moimenta da Beira | 3,536.72 mi (5,691.81 km) |
| Middle River to Moita | 3,532.27 mi (5,684.64 km) |
| Middle River to Moncao | 3,467.18 mi (5,579.88 km) |
