| Portimao to Olympia Heights (Florida) | 4,207.73 mi (6,771.69 km) |
| Portimao to Omaha (Nebraska) | 4,484.38 mi (7,216.91 km) |
| Portimao to On Top of the World Designated Place (Florida) | 4,197.55 mi (6,755.30 km) |
| Portimao to Onalaska (Wisconsin) | 4,182.79 mi (6,731.55 km) |
| Portimao to Oneida (New York) | 3,475.78 mi (5,593.72 km) |
| Portimao to Oneonta (New York) | 3,459.83 mi (5,568.06 km) |
| Portimao to Ontario (California) | 5,733.71 mi (9,227.52 km) |
| Portimao to Ontario (Oregon) | 5,265.91 mi (8,474.67 km) |
| Portimao to Opa-locka (Florida) | 4,197.17 mi (6,754.69 km) |
| Portimao to Opelika (Alabama) | 4,242.63 mi (6,827.85 km) |
| Portimao to Opelousas (Louisiana) | 4,658.74 mi (7,497.52 km) |
| Portimao to Orange (California) | 5,753.68 mi (9,259.66 km) |
| Portimao to Orange (Texas) | 4,758.78 mi (7,658.51 km) |
| Portimao to Orange City (Florida) | 4,150.25 mi (6,679.17 km) |
| Portimao to Orangeburg (South Carolina) | 3,983.82 mi (6,411.34 km) |
