Sir John Hawkins Hagarty (17 September 1816 – 27 April 1900) was a Canadian lawyer, teacher, and judge.

He was a student-at-law in the law office of George Duggan in Toronto.

He was called to the Bar in 1840 and was a partner with John Willoughby Crawford.

He was a judge for 41 years including: Puisne Judge of the Court of Common Pleas (1856–62), judge of the Court of Queen's Bench (1862–68), Chief Justice of Common Pleas (1868–78), Chief Justice of Queen's Bench (1878–84), and President of the Court of Appeal and Chief Justice of Ontario (1884–97).

He was knighted in the 1897 Diamond Jubilee Honours when he retired in 1897.