| Donegal to Octeville | 442.16 mi (711.59 km) |
| Donegal to Oignies | 547.81 mi (881.61 km) |
| Donegal to Oissel | 535.79 mi (862.27 km) |
| Donegal to Olivet | 637.12 mi (1,025.35 km) |
| Donegal to Ollioules | 1,013.43 mi (1,630.96 km) |
| Donegal to Olonne-sur-Mer | 625.38 mi (1,006.46 km) |
| Donegal to Oloron-Sainte-Marie | 860.79 mi (1,385.31 km) |
| Donegal to Onet Village | 855.78 mi (1,377.24 km) |
| Donegal to Onnaing | 572.68 mi (921.63 km) |
| Donegal to Orange | 927.24 mi (1,492.25 km) |
| Donegal to Orchies | 556.51 mi (895.62 km) |
| Donegal to Orleans | 635.29 mi (1,022.41 km) |
| Donegal to Orly | 606.34 mi (975.81 km) |
| Donegal to Ormesson-sur-Marne | 608.86 mi (979.86 km) |
| Donegal to Orsay | 602.21 mi (969.17 km) |
