| Harpenden to Octeville | 161.54 mi (259.97 km) |
| Harpenden to Oignies | 172.35 mi (277.38 km) |
| Harpenden to Oissel | 182.39 mi (293.53 km) |
| Harpenden to Olivet | 290.99 mi (468.31 km) |
| Harpenden to Ollioules | 665.24 mi (1,070.61 km) |
| Harpenden to Olonne-sur-Mer | 370.49 mi (596.24 km) |
| Harpenden to Oloron-Sainte-Marie | 595.93 mi (959.06 km) |
| Harpenden to Onet Village | 532.41 mi (856.83 km) |
| Harpenden to Onnaing | 197.78 mi (318.30 km) |
| Harpenden to Orange | 581.46 mi (935.78 km) |
| Harpenden to Orchies | 181.38 mi (291.91 km) |
| Harpenden to Orleans | 288.61 mi (464.47 km) |
| Harpenden to Orly | 244.48 mi (393.45 km) |
| Harpenden to Ormesson-sur-Marne | 245.22 mi (394.64 km) |
| Harpenden to Orsay | 242.95 mi (390.99 km) |
