| Ontario to Orangevale (California) | 378.88 mi (609.75 km) |
| Ontario to Orchards (Washington) | 845.78 mi (1,361.15 km) |
| Ontario to Orcutt (California) | 170.35 mi (274.16 km) |
| Ontario to Oregon (Ohio) | 1,923.38 mi (3,095.38 km) |
| Ontario to Oregon (Wisconsin) | 1,635.28 mi (2,631.72 km) |
| Ontario to Oregon City (Oregon) | 824.26 mi (1,326.52 km) |
| Ontario to Orem (Utah) | 540.79 mi (870.32 km) |
| Ontario to Orinda (California) | 368.47 mi (592.99 km) |
| Ontario to Orland Park (Illinois) | 1,695.71 mi (2,728.98 km) |
| Ontario to Orlando (Florida) | 2,164.88 mi (3,484.04 km) |
| Ontario to Ormond Beach (Florida) | 2,160.04 mi (3,476.24 km) |
| Ontario to Oro Valley (Arizona) | 399.06 mi (642.22 km) |
| Ontario to Oroville (California) | 436.13 mi (701.88 km) |
| Ontario to Oshkosh (Wisconsin) | 1,693.13 mi (2,724.83 km) |
| Ontario to Oskaloosa (Iowa) | 1,448.30 mi (2,330.82 km) |
