| Defiance to Olympia Heights (Florida) | 1,099.31 mi (1,769.16 km) |
| Defiance to Omaha (Nebraska) | 606.45 mi (975.99 km) |
| Defiance to On Top of the World Designated Place (Florida) | 849.32 mi (1,366.85 km) |
| Defiance to Onalaska (Wisconsin) | 391.72 mi (630.42 km) |
| Defiance to Oneida (New York) | 462.33 mi (744.05 km) |
| Defiance to Oneonta (New York) | 485.03 mi (780.58 km) |
| Defiance to Ontario (California) | 1,873.14 mi (3,014.53 km) |
| Defiance to Ontario (Oregon) | 1,657.00 mi (2,666.69 km) |
| Defiance to Opa-locka (Florida) | 1,088.42 mi (1,751.64 km) |
| Defiance to Opelika (Alabama) | 598.19 mi (962.69 km) |
| Defiance to Opelousas (Louisiana) | 858.65 mi (1,381.86 km) |
| Defiance to Orange (California) | 1,891.30 mi (3,043.75 km) |
| Defiance to Orange (Texas) | 932.65 mi (1,500.96 km) |
| Defiance to Orange City (Florida) | 870.45 mi (1,400.85 km) |
| Defiance to Orangeburg (South Carolina) | 571.24 mi (919.32 km) |
