| Ostrow Mazowiecka to Opwijk | 764.11 mi (1,229.72 km) |
| Ostrow Mazowiecka to Ostend | 812.03 mi (1,306.84 km) |
| Ostrow Mazowiecka to Oud-Heverlee | 746.61 mi (1,201.55 km) |
| Ostrow Mazowiecka to Oud-Turnhout | 724.21 mi (1,165.50 km) |
| Ostrow Mazowiecka to Oudenaarde | 790.77 mi (1,272.62 km) |
| Ostrow Mazowiecka to Oudenburg | 809.44 mi (1,302.66 km) |
| Ostrow Mazowiecka to Oupeye | 708.56 mi (1,140.31 km) |
| Ostrow Mazowiecka to Overijse | 753.20 mi (1,212.15 km) |
| Ostrow Mazowiecka to Overpelt | 707.90 mi (1,139.26 km) |
| Ostrow Mazowiecka to Paal | 721.41 mi (1,161.01 km) |
| Ostrow Mazowiecka to Peer | 707.92 mi (1,139.28 km) |
| Ostrow Mazowiecka to Pepinster | 704.44 mi (1,133.69 km) |
| Ostrow Mazowiecka to Peruwelz | 798.47 mi (1,285.01 km) |
| Ostrow Mazowiecka to Perwez | 744.83 mi (1,198.69 km) |
| Ostrow Mazowiecka to Philippeville | 765.51 mi (1,231.97 km) |
