| Porsgrunn to Orbetello | 1,154.01 mi (1,857.20 km) |
| Porsgrunn to Oria | 1,331.65 mi (2,143.08 km) |
| Porsgrunn to Oristano | 1,328.17 mi (2,137.48 km) |
| Porsgrunn to Orta Nova | 1,255.90 mi (2,021.18 km) |
| Porsgrunn to Orte | 1,156.46 mi (1,861.14 km) |
| Porsgrunn to Ortona | 1,175.70 mi (1,892.10 km) |
| Porsgrunn to Orvieto | 1,137.57 mi (1,830.75 km) |
| Porsgrunn to Orzinuovi | 947.70 mi (1,525.18 km) |
| Porsgrunn to Osimo | 1,091.89 mi (1,757.22 km) |
| Porsgrunn to Ospitaletto | 937.05 mi (1,508.03 km) |
| Porsgrunn to Ostuni | 1,315.34 mi (2,116.84 km) |
| Porsgrunn to Ottaviano | 1,278.89 mi (2,058.17 km) |
| Porsgrunn to Ovada | 1,001.22 mi (1,611.31 km) |
| Porsgrunn to Ozieri | 1,280.72 mi (2,061.11 km) |
| Porsgrunn to Paceco | 1,465.55 mi (2,358.57 km) |
