| Greenock to Oerlinghausen | 610.09 mi (981.84 km) |
| Greenock to Oestrich-Winkel | 669.88 mi (1,078.06 km) |
| Greenock to Offenburg | 743.77 mi (1,196.99 km) |
| Greenock to Oftersheim | 718.77 mi (1,156.75 km) |
| Greenock to Ohrdruf | 727.80 mi (1,171.29 km) |
| Greenock to Ohringen | 756.69 mi (1,217.77 km) |
| Greenock to Olbernhau | 828.25 mi (1,332.94 km) |
| Greenock to Olching | 864.29 mi (1,390.95 km) |
| Greenock to Oldenburg | 554.08 mi (891.71 km) |
| Greenock to Oldenburg in Holstein | 627.21 mi (1,009.40 km) |
| Greenock to Olfen | 574.09 mi (923.90 km) |
| Greenock to Olpe | 618.63 mi (995.60 km) |
| Greenock to Olsberg | 627.29 mi (1,009.53 km) |
| Greenock to Oranienburg | 755.27 mi (1,215.49 km) |
| Greenock to Ortenberg | 688.94 mi (1,108.74 km) |
