| Knoxville to Orbetello | 4,834.04 mi (7,779.64 km) |
| Knoxville to Oria | 5,185.82 mi (8,345.77 km) |
| Knoxville to Oristano | 4,805.93 mi (7,734.39 km) |
| Knoxville to Orta Nova | 5,070.57 mi (8,160.30 km) |
| Knoxville to Orte | 4,884.46 mi (7,860.78 km) |
| Knoxville to Ortona | 4,975.55 mi (8,007.38 km) |
| Knoxville to Orvieto | 4,863.20 mi (7,826.56 km) |
| Knoxville to Orzinuovi | 4,676.46 mi (7,526.04 km) |
| Knoxville to Osimo | 4,894.54 mi (7,877.00 km) |
| Knoxville to Ospitaletto | 4,677.14 mi (7,527.13 km) |
| Knoxville to Ostuni | 5,174.47 mi (8,327.50 km) |
| Knoxville to Ottaviano | 5,035.18 mi (8,103.34 km) |
| Knoxville to Ovada | 4,646.95 mi (7,478.54 km) |
| Knoxville to Ozieri | 4,800.95 mi (7,726.39 km) |
| Knoxville to Paceco | 5,056.66 mi (8,137.92 km) |
