Ontario County is a county in the U.S. State of New York. As of the 2020 census, the population was 112,458. The county seat is Canandaigua. Ontario County is part of the Rochester, NY Metropolitan Statistical Area. In 2006, Progressive Farmer rated Ontario County as the "Best Place to Live" in the U.S., for its "great schools, low crime, excellent health care" and its proximity to Rochester.