| Ontario to Oakleaf Plantation (Florida) | 2,100.05 mi (3,379.70 km) |
| Ontario to Oakley (California) | 356.05 mi (573.01 km) |
| Ontario to Oakton (Virginia) | 2,246.15 mi (3,614.83 km) |
| Ontario to Oakville (Missouri) | 1,544.78 mi (2,486.08 km) |
| Ontario to Oatfield (Oregon) | 828.87 mi (1,333.93 km) |
| Ontario to Ocala (Florida) | 2,102.56 mi (3,383.75 km) |
| Ontario to Ocean Acres (New Jersey) | 2,402.73 mi (3,866.82 km) |
| Ontario to Ocean City (New Jersey) | 2,388.38 mi (3,843.73 km) |
| Ontario to Ocean Pines (Maryland) | 2,364.98 mi (3,806.06 km) |
| Ontario to Ocean Pointe (Hawaii) | 2,605.25 mi (4,192.74 km) |
| Ontario to Ocean Springs (Mississippi) | 1,697.46 mi (2,731.80 km) |
| Ontario to Oceanside (California) | 58.84 mi (94.69 km) |
| Ontario to Oceanside (New York) | 2,432.27 mi (3,914.37 km) |
| Ontario to Ocoee (Florida) | 2,151.30 mi (3,462.18 km) |
| Ontario to Oconomowoc (Wisconsin) | 1,681.99 mi (2,706.90 km) |
