| Port Huron to Oerlinghausen | 4,014.96 mi (6,461.45 km) |
| Port Huron to Oestrich-Winkel | 4,059.73 mi (6,533.51 km) |
| Port Huron to Offenburg | 4,112.59 mi (6,618.58 km) |
| Port Huron to Oftersheim | 4,104.74 mi (6,605.94 km) |
| Port Huron to Ohrdruf | 4,131.97 mi (6,649.76 km) |
| Port Huron to Ohringen | 4,145.95 mi (6,672.25 km) |
| Port Huron to Olbernhau | 4,233.29 mi (6,812.82 km) |
| Port Huron to Olching | 4,253.08 mi (6,844.68 km) |
| Port Huron to Oldenburg | 3,957.75 mi (6,369.38 km) |
| Port Huron to Oldenburg in Holstein | 4,012.09 mi (6,456.84 km) |
| Port Huron to Olfen | 3,976.30 mi (6,399.24 km) |
| Port Huron to Olpe | 4,017.42 mi (6,465.41 km) |
| Port Huron to Olsberg | 4,029.90 mi (6,485.50 km) |
| Port Huron to Oranienburg | 4,150.47 mi (6,679.54 km) |
| Port Huron to Ortenberg | 4,086.80 mi (6,577.07 km) |
