| Mentor to Olympia Heights (Florida) | 1,104.56 mi (1,777.62 km) |
| Mentor to Omaha (Nebraska) | 761.48 mi (1,225.49 km) |
| Mentor to On Top of the World Designated Place (Florida) | 871.07 mi (1,401.84 km) |
| Mentor to Onalaska (Wisconsin) | 522.70 mi (841.20 km) |
| Mentor to Oneida (New York) | 304.96 mi (490.79 km) |
| Mentor to Oneonta (New York) | 325.80 mi (524.33 km) |
| Mentor to Ontario (California) | 2,031.48 mi (3,269.35 km) |
| Mentor to Ontario (Oregon) | 1,798.20 mi (2,893.92 km) |
| Mentor to Opa-locka (Florida) | 1,092.69 mi (1,758.52 km) |
| Mentor to Opelika (Alabama) | 662.04 mi (1,065.46 km) |
| Mentor to Opelousas (Louisiana) | 975.43 mi (1,569.80 km) |
| Mentor to Orange (California) | 2,049.72 mi (3,298.70 km) |
| Mentor to Orange (Texas) | 1,057.02 mi (1,701.10 km) |
| Mentor to Orange City (Florida) | 881.25 mi (1,418.24 km) |
| Mentor to Orangeburg (South Carolina) | 566.90 mi (912.34 km) |
