| Key West to Olympia Heights (Florida) | 120.49 mi (193.91 km) |
| Key West to Omaha (Nebraska) | 1,415.88 mi (2,278.63 km) |
| Key West to On Top of the World Designated Place (Florida) | 315.36 mi (507.52 km) |
| Key West to Onalaska (Wisconsin) | 1,437.38 mi (2,313.24 km) |
| Key West to Oneida (New York) | 1,325.43 mi (2,133.07 km) |
| Key West to Oneonta (New York) | 1,294.08 mi (2,082.62 km) |
| Key West to Ontario (California) | 2,242.95 mi (3,609.68 km) |
| Key West to Ontario (Oregon) | 2,389.52 mi (3,845.55 km) |
| Key West to Opa-locka (Florida) | 132.54 mi (213.31 km) |
| Key West to Opelika (Alabama) | 600.41 mi (966.27 km) |
| Key West to Opelousas (Louisiana) | 753.14 mi (1,212.06 km) |
| Key West to Orange (California) | 2,253.21 mi (3,626.19 km) |
| Key West to Orange (Texas) | 828.97 mi (1,334.10 km) |
| Key West to Orange City (Florida) | 303.48 mi (488.41 km) |
| Key West to Orangeburg (South Carolina) | 619.34 mi (996.74 km) |
