| Monaghan to Octeville | 391.48 mi (630.02 km) |
| Monaghan to Oignies | 494.25 mi (795.42 km) |
| Monaghan to Oissel | 482.75 mi (776.91 km) |
| Monaghan to Olivet | 584.77 mi (941.10 km) |
| Monaghan to Ollioules | 961.65 mi (1,547.63 km) |
| Monaghan to Olonne-sur-Mer | 579.55 mi (932.70 km) |
| Monaghan to Oloron-Sainte-Marie | 816.15 mi (1,313.47 km) |
| Monaghan to Onet Village | 805.78 mi (1,296.77 km) |
| Monaghan to Onnaing | 519.21 mi (835.59 km) |
| Monaghan to Orange | 875.55 mi (1,409.06 km) |
| Monaghan to Orchies | 503.01 mi (809.52 km) |
| Monaghan to Orleans | 582.90 mi (938.09 km) |
| Monaghan to Orly | 553.09 mi (890.11 km) |
| Monaghan to Ormesson-sur-Marne | 555.53 mi (894.04 km) |
| Monaghan to Orsay | 549.08 mi (883.65 km) |
