| Hemel Hempstead to Orbetello | 844.06 mi (1,358.39 km) |
| Hemel Hempstead to Oria | 1,158.62 mi (1,864.62 km) |
| Hemel Hempstead to Oristano | 925.88 mi (1,490.05 km) |
| Hemel Hempstead to Orta Nova | 1,049.13 mi (1,688.40 km) |
| Hemel Hempstead to Orte | 879.36 mi (1,415.20 km) |
| Hemel Hempstead to Ortona | 951.65 mi (1,531.54 km) |
| Hemel Hempstead to Orvieto | 856.68 mi (1,378.69 km) |
| Hemel Hempstead to Orzinuovi | 646.00 mi (1,039.63 km) |
| Hemel Hempstead to Osimo | 862.67 mi (1,388.33 km) |
| Hemel Hempstead to Ospitaletto | 642.98 mi (1,034.78 km) |
| Hemel Hempstead to Ostuni | 1,144.89 mi (1,842.53 km) |
| Hemel Hempstead to Ottaviano | 1,033.63 mi (1,663.46 km) |
| Hemel Hempstead to Ovada | 645.40 mi (1,038.67 km) |
| Hemel Hempstead to Ozieri | 893.20 mi (1,437.47 km) |
| Hemel Hempstead to Paceco | 1,141.44 mi (1,836.97 km) |
