| Ottawa to Olympia (Washington) | 1,718.21 mi (2,765.19 km) |
| Ottawa to Olympia Heights (Florida) | 1,183.97 mi (1,905.42 km) |
| Ottawa to Omaha (Nebraska) | 375.02 mi (603.53 km) |
| Ottawa to On Top of the World Designated Place (Florida) | 922.61 mi (1,484.80 km) |
| Ottawa to Onalaska (Wisconsin) | 212.78 mi (342.43 km) |
| Ottawa to Oneida (New York) | 683.29 mi (1,099.65 km) |
| Ottawa to Oneonta (New York) | 710.82 mi (1,143.96 km) |
| Ottawa to Ontario (California) | 1,643.80 mi (2,645.44 km) |
| Ottawa to Ontario (Oregon) | 1,434.37 mi (2,308.39 km) |
| Ottawa to Opa-locka (Florida) | 1,174.71 mi (1,890.52 km) |
| Ottawa to Opelika (Alabama) | 629.99 mi (1,013.87 km) |
| Ottawa to Opelousas (Louisiana) | 769.98 mi (1,239.16 km) |
| Ottawa to Orange (California) | 1,662.12 mi (2,674.93 km) |
| Ottawa to Orange (Texas) | 823.59 mi (1,325.44 km) |
| Ottawa to Orange City (Florida) | 957.08 mi (1,540.27 km) |
