| Rio Maior to Orbetello | 1,071.28 mi (1,724.06 km) |
| Rio Maior to Oria | 1,404.83 mi (2,260.86 km) |
| Rio Maior to Oristano | 932.06 mi (1,500.00 km) |
| Rio Maior to Orta Nova | 1,300.94 mi (2,093.67 km) |
| Rio Maior to Orte | 1,131.05 mi (1,820.25 km) |
| Rio Maior to Ortona | 1,233.29 mi (1,984.79 km) |
| Rio Maior to Orvieto | 1,118.43 mi (1,799.93 km) |
| Rio Maior to Orzinuovi | 1,047.12 mi (1,685.18 km) |
| Rio Maior to Osimo | 1,192.52 mi (1,919.18 km) |
| Rio Maior to Ospitaletto | 1,056.76 mi (1,700.69 km) |
| Rio Maior to Ostuni | 1,400.80 mi (2,254.36 km) |
| Rio Maior to Ottaviano | 1,238.16 mi (1,992.63 km) |
| Rio Maior to Ovada | 971.94 mi (1,564.18 km) |
| Rio Maior to Ozieri | 952.19 mi (1,532.41 km) |
| Rio Maior to Paceco | 1,160.12 mi (1,867.03 km) |
