| Castlebar to Octeville | 438.71 mi (706.03 km) |
| Castlebar to Oignies | 570.26 mi (917.74 km) |
| Castlebar to Oissel | 543.49 mi (874.67 km) |
| Castlebar to Olivet | 639.19 mi (1,028.68 km) |
| Castlebar to Ollioules | 1,010.55 mi (1,626.32 km) |
| Castlebar to Olonne-sur-Mer | 605.00 mi (973.66 km) |
| Castlebar to Oloron-Sainte-Marie | 836.04 mi (1,345.47 km) |
| Castlebar to Onet Village | 846.04 mi (1,361.56 km) |
| Castlebar to Onnaing | 596.28 mi (959.62 km) |
| Castlebar to Orange | 924.23 mi (1,487.41 km) |
| Castlebar to Orchies | 579.73 mi (932.99 km) |
| Castlebar to Orleans | 637.60 mi (1,026.12 km) |
| Castlebar to Orly | 615.28 mi (990.20 km) |
| Castlebar to Ormesson-sur-Marne | 618.58 mi (995.51 km) |
| Castlebar to Orsay | 610.11 mi (981.88 km) |
