| Greenock to Orbetello | 1,173.78 mi (1,889.02 km) |
| Greenock to Oria | 1,471.13 mi (2,367.55 km) |
| Greenock to Oristano | 1,264.34 mi (2,034.76 km) |
| Greenock to Orta Nova | 1,365.96 mi (2,198.30 km) |
| Greenock to Orte | 1,204.84 mi (1,939.00 km) |
| Greenock to Ortona | 1,269.42 mi (2,042.94 km) |
| Greenock to Orvieto | 1,182.23 mi (1,902.62 km) |
| Greenock to Orzinuovi | 968.38 mi (1,558.46 km) |
| Greenock to Osimo | 1,178.84 mi (1,897.16 km) |
| Greenock to Ospitaletto | 963.73 mi (1,550.98 km) |
| Greenock to Ostuni | 1,456.56 mi (2,344.11 km) |
| Greenock to Ottaviano | 1,357.14 mi (2,184.10 km) |
| Greenock to Ovada | 976.79 mi (1,572.00 km) |
| Greenock to Ozieri | 1,231.04 mi (1,981.16 km) |
| Greenock to Paceco | 1,476.63 mi (2,376.41 km) |
