| Gloucester to Orbetello | 904.90 mi (1,456.29 km) |
| Gloucester to Oria | 1,226.13 mi (1,973.26 km) |
| Gloucester to Oristano | 974.56 mi (1,568.39 km) |
| Gloucester to Orta Nova | 1,115.48 mi (1,795.20 km) |
| Gloucester to Orte | 942.57 mi (1,516.92 km) |
| Gloucester to Ortona | 1,017.94 mi (1,638.21 km) |
| Gloucester to Orvieto | 919.92 mi (1,480.48 km) |
| Gloucester to Orzinuovi | 711.66 mi (1,145.30 km) |
| Gloucester to Osimo | 929.78 mi (1,496.33 km) |
| Gloucester to Ospitaletto | 709.35 mi (1,141.58 km) |
| Gloucester to Ostuni | 1,212.67 mi (1,951.61 km) |
| Gloucester to Ottaviano | 1,097.35 mi (1,766.02 km) |
| Gloucester to Ovada | 705.87 mi (1,135.99 km) |
| Gloucester to Ozieri | 944.44 mi (1,519.92 km) |
| Gloucester to Paceco | 1,196.66 mi (1,925.83 km) |
