| South Portland to Nuth | 3,444.95 mi (5,544.11 km) |
| South Portland to Oegstgeest | 3,355.48 mi (5,400.13 km) |
| South Portland to Oirschot | 3,406.07 mi (5,481.54 km) |
| South Portland to Oisterwijk | 3,399.91 mi (5,471.63 km) |
| South Portland to Oldebroek | 3,404.95 mi (5,479.74 km) |
| South Portland to Oldenzaal | 3,448.76 mi (5,550.24 km) |
| South Portland to Ommen | 3,423.36 mi (5,509.37 km) |
| South Portland to Oosterend | 3,397.21 mi (5,467.28 km) |
| South Portland to Oosterhout | 3,384.72 mi (5,447.18 km) |
| South Portland to Oosterwolde | 3,406.25 mi (5,481.82 km) |
| South Portland to Oostzaan | 3,365.58 mi (5,416.38 km) |
| South Portland to Opmeer | 3,361.50 mi (5,409.82 km) |
| South Portland to Oss | 3,407.67 mi (5,484.11 km) |
| South Portland to Oud-Beijerland | 3,362.11 mi (5,410.79 km) |
| South Portland to Oudenbosch | 3,372.86 mi (5,428.09 km) |
