| Houston to Olympia Heights (Florida) | 961.16 mi (1,546.83 km) |
| Houston to Omaha (Nebraska) | 793.84 mi (1,277.55 km) |
| Houston to On Top of the World Designated Place (Florida) | 789.29 mi (1,270.24 km) |
| Houston to Onalaska (Wisconsin) | 1,001.06 mi (1,611.05 km) |
| Houston to Oneida (New York) | 1,423.84 mi (2,291.45 km) |
| Houston to Oneonta (New York) | 1,426.28 mi (2,295.38 km) |
| Houston to Ontario (California) | 1,332.93 mi (2,145.14 km) |
| Houston to Ontario (Oregon) | 1,537.72 mi (2,474.72 km) |
| Houston to Opa-locka (Florida) | 961.89 mi (1,548.01 km) |
| Houston to Opelika (Alabama) | 623.69 mi (1,003.73 km) |
| Houston to Opelousas (Louisiana) | 204.05 mi (328.38 km) |
| Houston to Orange (California) | 1,343.45 mi (2,162.07 km) |
| Houston to Orange (Texas) | 100.18 mi (161.23 km) |
| Houston to Orange City (Florida) | 850.61 mi (1,368.92 km) |
| Houston to Orangeburg (South Carolina) | 890.86 mi (1,433.70 km) |
