| Difficult Run to Nuth | 3,935.22 mi (6,333.13 km) |
| Difficult Run to Oegstgeest | 3,846.05 mi (6,189.62 km) |
| Difficult Run to Oirschot | 3,896.50 mi (6,270.82 km) |
| Difficult Run to Oisterwijk | 3,890.36 mi (6,260.93 km) |
| Difficult Run to Oldebroek | 3,895.63 mi (6,269.41 km) |
| Difficult Run to Oldenzaal | 3,939.45 mi (6,339.93 km) |
| Difficult Run to Ommen | 3,914.06 mi (6,299.07 km) |
| Difficult Run to Oosterend | 3,887.92 mi (6,257.01 km) |
| Difficult Run to Oosterhout | 3,875.16 mi (6,236.47 km) |
| Difficult Run to Oosterwolde | 3,896.95 mi (6,271.54 km) |
| Difficult Run to Oostzaan | 3,856.23 mi (6,205.99 km) |
| Difficult Run to Opmeer | 3,852.18 mi (6,199.49 km) |
| Difficult Run to Oss | 3,898.20 mi (6,273.54 km) |
| Difficult Run to Oud-Beijerland | 3,852.57 mi (6,200.12 km) |
| Difficult Run to Oudenbosch | 3,863.25 mi (6,217.30 km) |
