Ontario, OH has a population of 6,117 and is the 5,683rd largest city in the United States. The population density is 553 per sq mi which is 115% higher than the Ohio average and 510% higher than the national average. The median age in Ontario is 46 which is approximately 17% higher than the Ohio average of 39. In Ontario, 67% of the population over 15 years of age are married, 90% speak English and 2% speak Spanish. 71% of Ontario residents were born in Ohio, 21% were born out of state, 0% were born outside of the United States and 7% were foreign born.