| Ottawa to Opwijk | 4,198.32 mi (6,756.54 km) |
| Ottawa to Ostend | 4,141.94 mi (6,665.82 km) |
| Ottawa to Oud-Heverlee | 4,221.12 mi (6,793.24 km) |
| Ottawa to Oud-Turnhout | 4,215.62 mi (6,784.39 km) |
| Ottawa to Oudenaarde | 4,180.56 mi (6,727.97 km) |
| Ottawa to Oudenburg | 4,146.43 mi (6,673.04 km) |
| Ottawa to Oupeye | 4,262.02 mi (6,859.06 km) |
| Ottawa to Overijse | 4,217.92 mi (6,788.09 km) |
| Ottawa to Overpelt | 4,235.22 mi (6,815.93 km) |
| Ottawa to Paal | 4,232.58 mi (6,811.68 km) |
| Ottawa to Peer | 4,239.61 mi (6,822.99 km) |
| Ottawa to Pepinster | 4,273.65 mi (6,877.77 km) |
| Ottawa to Peruwelz | 4,191.65 mi (6,745.81 km) |
| Ottawa to Perwez | 4,234.16 mi (6,814.23 km) |
| Ottawa to Philippeville | 4,239.44 mi (6,822.72 km) |
