| Castelo Branco to Orbetello | 988.46 mi (1,590.78 km) |
| Castelo Branco to Oria | 1,323.53 mi (2,130.01 km) |
| Castelo Branco to Oristano | 852.30 mi (1,371.64 km) |
| Castelo Branco to Orta Nova | 1,218.99 mi (1,961.78 km) |
| Castelo Branco to Orte | 1,048.26 mi (1,687.01 km) |
| Castelo Branco to Ortona | 1,150.60 mi (1,851.72 km) |
| Castelo Branco to Orvieto | 1,035.48 mi (1,666.45 km) |
| Castelo Branco to Orzinuovi | 964.24 mi (1,551.79 km) |
| Castelo Branco to Osimo | 1,109.32 mi (1,785.28 km) |
| Castelo Branco to Ospitaletto | 973.95 mi (1,567.42 km) |
| Castelo Branco to Ostuni | 1,319.28 mi (2,123.17 km) |
| Castelo Branco to Ottaviano | 1,156.70 mi (1,861.53 km) |
| Castelo Branco to Ovada | 888.81 mi (1,430.41 km) |
| Castelo Branco to Ozieri | 871.26 mi (1,402.16 km) |
| Castelo Branco to Paceco | 1,083.23 mi (1,743.29 km) |
