| Dumbarton to Orbetello | 1,168.47 mi (1,880.47 km) |
| Dumbarton to Oria | 1,465.02 mi (2,357.72 km) |
| Dumbarton to Oristano | 1,260.03 mi (2,027.83 km) |
| Dumbarton to Orta Nova | 1,360.02 mi (2,188.74 km) |
| Dumbarton to Orte | 1,199.29 mi (1,930.07 km) |
| Dumbarton to Ortona | 1,263.53 mi (2,033.46 km) |
| Dumbarton to Orvieto | 1,176.69 mi (1,893.70 km) |
| Dumbarton to Orzinuovi | 962.76 mi (1,549.41 km) |
| Dumbarton to Osimo | 1,172.91 mi (1,887.62 km) |
| Dumbarton to Ospitaletto | 958.05 mi (1,541.83 km) |
| Dumbarton to Ostuni | 1,450.43 mi (2,334.24 km) |
| Dumbarton to Ottaviano | 1,351.47 mi (2,174.97 km) |
| Dumbarton to Ovada | 971.64 mi (1,563.70 km) |
| Dumbarton to Ozieri | 1,226.53 mi (1,973.91 km) |
| Dumbarton to Paceco | 1,471.72 mi (2,368.50 km) |
