| Manassas to Olympia Heights (Florida) | 915.06 mi (1,472.64 km) |
| Manassas to Omaha (Nebraska) | 996.00 mi (1,602.91 km) |
| Manassas to On Top of the World Designated Place (Florida) | 720.56 mi (1,159.63 km) |
| Manassas to Onalaska (Wisconsin) | 794.44 mi (1,278.52 km) |
| Manassas to Oneida (New York) | 313.84 mi (505.08 km) |
| Manassas to Oneonta (New York) | 285.78 mi (459.92 km) |
| Manassas to Ontario (California) | 2,237.09 mi (3,600.24 km) |
| Manassas to Ontario (Oregon) | 2,059.17 mi (3,313.91 km) |
| Manassas to Opa-locka (Florida) | 902.22 mi (1,451.98 km) |
| Manassas to Opelika (Alabama) | 610.25 mi (982.10 km) |
| Manassas to Opelousas (Louisiana) | 1,003.67 mi (1,615.25 km) |
| Manassas to Orange (California) | 2,254.33 mi (3,627.99 km) |
| Manassas to Orange (Texas) | 1,099.88 mi (1,770.08 km) |
| Manassas to Orange City (Florida) | 712.11 mi (1,146.02 km) |
| Manassas to Orangeburg (South Carolina) | 409.17 mi (658.50 km) |
