| Belfast to Oerlinghausen | 628.44 mi (1,011.37 km) |
| Belfast to Oestrich-Winkel | 667.17 mi (1,073.71 km) |
| Belfast to Offenburg | 728.99 mi (1,173.19 km) |
| Belfast to Oftersheim | 713.47 mi (1,148.22 km) |
| Belfast to Ohrdruf | 742.30 mi (1,194.61 km) |
| Belfast to Ohringen | 753.85 mi (1,213.21 km) |
| Belfast to Olbernhau | 849.02 mi (1,366.36 km) |
| Belfast to Olching | 861.53 mi (1,386.50 km) |
| Belfast to Oldenburg | 583.83 mi (939.59 km) |
| Belfast to Oldenburg in Holstein | 674.15 mi (1,084.94 km) |
| Belfast to Olfen | 585.27 mi (941.90 km) |
| Belfast to Olpe | 624.47 mi (1,004.98 km) |
| Belfast to Olsberg | 638.86 mi (1,028.14 km) |
| Belfast to Oranienburg | 792.15 mi (1,274.85 km) |
| Belfast to Ortenberg | 693.56 mi (1,116.18 km) |
