| Merthyr Tudful to Smolyan | 1,492.05 mi (2,401.22 km) |
| Merthyr Tudful to Sofia | 1,389.62 mi (2,236.38 km) |
| Merthyr Tudful to Sopot | 1,450.23 mi (2,333.91 km) |
| Merthyr Tudful to Sozopol | 1,582.41 mi (2,546.64 km) |
| Merthyr Tudful to Sredets | 1,564.13 mi (2,517.22 km) |
| Merthyr Tudful to Stamboliyski | 1,462.27 mi (2,353.30 km) |
| Merthyr Tudful to Stara Zagora | 1,496.23 mi (2,407.95 km) |
| Merthyr Tudful to Svilengrad | 1,546.13 mi (2,488.26 km) |
| Merthyr Tudful to Svishtov | 1,437.64 mi (2,313.65 km) |
| Merthyr Tudful to Targovishte | 1,503.27 mi (2,419.28 km) |
| Merthyr Tudful to Teteven | 1,419.58 mi (2,284.59 km) |
| Merthyr Tudful to Troyan | 1,439.56 mi (2,316.75 km) |
| Merthyr Tudful to Tryavna | 1,472.78 mi (2,370.21 km) |
| Merthyr Tudful to Tutrakan | 1,474.89 mi (2,373.61 km) |
| Merthyr Tudful to Varna | 1,560.64 mi (2,511.61 km) |
