| Belfast to Orbetello | 1,143.37 mi (1,840.08 km) |
| Belfast to Oria | 1,455.64 mi (2,342.63 km) |
| Belfast to Oristano | 1,217.07 mi (1,958.69 km) |
| Belfast to Orta Nova | 1,347.20 mi (2,168.10 km) |
| Belfast to Orte | 1,178.74 mi (1,896.99 km) |
| Belfast to Ortona | 1,249.85 mi (2,011.44 km) |
| Belfast to Orvieto | 1,156.05 mi (1,860.49 km) |
| Belfast to Orzinuovi | 944.81 mi (1,520.53 km) |
| Belfast to Osimo | 1,160.35 mi (1,867.40 km) |
| Belfast to Ospitaletto | 941.45 mi (1,515.12 km) |
| Belfast to Ostuni | 1,441.65 mi (2,320.12 km) |
| Belfast to Ottaviano | 1,332.88 mi (2,145.07 km) |
| Belfast to Ovada | 944.57 mi (1,520.14 km) |
| Belfast to Ozieri | 1,186.94 mi (1,910.19 km) |
| Belfast to Paceco | 1,438.42 mi (2,314.91 km) |
