| Fort Collins to Oerlinghausen | 4,913.79 mi (7,907.98 km) |
| Fort Collins to Oestrich-Winkel | 4,984.65 mi (8,022.01 km) |
| Fort Collins to Offenburg | 5,054.55 mi (8,134.51 km) |
| Fort Collins to Oftersheim | 5,033.42 mi (8,100.50 km) |
| Fort Collins to Ohrdruf | 5,032.54 mi (8,099.09 km) |
| Fort Collins to Ohringen | 5,071.44 mi (8,161.69 km) |
| Fort Collins to Olbernhau | 5,120.66 mi (8,240.90 km) |
| Fort Collins to Olching | 5,178.95 mi (8,334.71 km) |
| Fort Collins to Oldenburg | 4,844.91 mi (7,797.14 km) |
| Fort Collins to Oldenburg in Holstein | 4,870.70 mi (7,838.64 km) |
| Fort Collins to Olfen | 4,884.89 mi (7,861.47 km) |
| Fort Collins to Olpe | 4,931.74 mi (7,936.87 km) |
| Fort Collins to Olsberg | 4,936.91 mi (7,945.18 km) |
| Fort Collins to Oranienburg | 5,014.49 mi (8,070.04 km) |
| Fort Collins to Ortenberg | 5,002.01 mi (8,049.96 km) |
