| Gaithersburg to Olympia Heights (Florida) | 944.16 mi (1,519.48 km) |
| Gaithersburg to Omaha (Nebraska) | 1,003.04 mi (1,614.23 km) |
| Gaithersburg to On Top of the World Designated Place (Florida) | 750.89 mi (1,208.44 km) |
| Gaithersburg to Onalaska (Wisconsin) | 793.71 mi (1,277.35 km) |
| Gaithersburg to Oneida (New York) | 284.09 mi (457.19 km) |
| Gaithersburg to Oneonta (New York) | 255.40 mi (411.03 km) |
| Gaithersburg to Ontario (California) | 2,249.71 mi (3,620.56 km) |
| Gaithersburg to Ontario (Oregon) | 2,062.24 mi (3,318.86 km) |
| Gaithersburg to Opa-locka (Florida) | 931.29 mi (1,498.77 km) |
| Gaithersburg to Opelika (Alabama) | 638.86 mi (1,028.14 km) |
| Gaithersburg to Opelousas (Louisiana) | 1,029.74 mi (1,657.20 km) |
| Gaithersburg to Orange (California) | 2,267.09 mi (3,648.53 km) |
| Gaithersburg to Orange (Texas) | 1,125.33 mi (1,811.04 km) |
| Gaithersburg to Orange City (Florida) | 742.12 mi (1,194.33 km) |
| Gaithersburg to Orangeburg (South Carolina) | 439.60 mi (707.46 km) |
