| Grefrath to Oestrich-Winkel | 117.48 mi (189.07 km) |
| Grefrath to Offenburg | 210.54 mi (338.84 km) |
| Grefrath to Oftersheim | 168.01 mi (270.38 km) |
| Grefrath to Ohrdruf | 193.81 mi (311.91 km) |
| Grefrath to Ohringen | 203.07 mi (326.81 km) |
| Grefrath to Olbernhau | 307.41 mi (494.74 km) |
| Grefrath to Olching | 310.14 mi (499.12 km) |
| Grefrath to Oldenburg | 147.90 mi (238.03 km) |
| Grefrath to Oldenburg in Holstein | 279.01 mi (449.03 km) |
| Grefrath to Olfen | 51.95 mi (83.61 km) |
| Grefrath to Olpe | 68.32 mi (109.94 km) |
| Grefrath to Olsberg | 92.47 mi (148.82 km) |
| Grefrath to Oranienburg | 308.85 mi (497.05 km) |
| Grefrath to Ortenberg | 136.42 mi (219.54 km) |
| Grefrath to Oschatz | 292.10 mi (470.09 km) |
