| Merthyr Tudful to Sesena | 804.35 mi (1,294.48 km) |
| Merthyr Tudful to Sestao | 582.87 mi (938.03 km) |
| Merthyr Tudful to Sevilla | 1,010.12 mi (1,625.64 km) |
| Merthyr Tudful to Sevilla La Nueva | 787.96 mi (1,268.10 km) |
| Merthyr Tudful to Silla | 867.23 mi (1,395.68 km) |
| Merthyr Tudful to Silleda | 664.68 mi (1,069.70 km) |
| Merthyr Tudful to Sitges | 766.32 mi (1,233.27 km) |
| Merthyr Tudful to Socuellamos | 860.65 mi (1,385.08 km) |
| Merthyr Tudful to Soller | 877.06 mi (1,411.49 km) |
| Merthyr Tudful to Solsona | 711.75 mi (1,145.44 km) |
| Merthyr Tudful to Son Servera | 897.55 mi (1,444.47 km) |
| Merthyr Tudful to Sonseca | 832.54 mi (1,339.85 km) |
| Merthyr Tudful to Sopelana | 578.03 mi (930.24 km) |
| Merthyr Tudful to Soria | 690.63 mi (1,111.46 km) |
| Merthyr Tudful to Suances | 574.99 mi (925.36 km) |
