Prescott County is known as a historic county in the Canadian province of Ontario.
It was created in 1800 from a portion of Glengarry County. It was named in honour of Major General Robert Prescott, Governor of Canada at that time. First settlers were Americans, but not all were Loyalists. In 1820, the county was united with Russell County to form United Counties of Prescott and Russell which is still an upper-tier municipality.