| South Portland to Oerlinghausen | 3,525.83 mi (5,674.27 km) |
| South Portland to Oestrich-Winkel | 3,555.80 mi (5,722.51 km) |
| South Portland to Offenburg | 3,598.80 mi (5,791.71 km) |
| South Portland to Oftersheim | 3,598.07 mi (5,790.54 km) |
| South Portland to Ohrdruf | 3,639.77 mi (5,857.65 km) |
| South Portland to Ohringen | 3,640.30 mi (5,858.50 km) |
| South Portland to Olbernhau | 3,746.30 mi (6,029.09 km) |
| South Portland to Olching | 3,745.57 mi (6,027.92 km) |
| South Portland to Oldenburg | 3,476.07 mi (5,594.19 km) |
| South Portland to Oldenburg in Holstein | 3,544.90 mi (5,704.97 km) |
| South Portland to Olfen | 3,482.60 mi (5,604.70 km) |
| South Portland to Olpe | 3,519.88 mi (5,664.70 km) |
| South Portland to Olsberg | 3,536.09 mi (5,690.78 km) |
| South Portland to Oranienburg | 3,677.50 mi (5,918.36 km) |
| South Portland to Ortenberg | 3,587.59 mi (5,773.66 km) |
