The 22-year-old Chun led from start to finish and her 21-under-par total of 263 broke the previous record low score by two shots.
It is also one better than the men's majors best of 20-under set by Jason Day at last year's PGA Championship at Whistling Straits and then matched by Henrik Stenson at this summer's British Open Championship at Royal Troon.
Victory by four shots from fellow South Koreans Ryu So Yeon (66) and Park Sung Hyun (69) gave the popular Chun her second major after winning last year's U.S. Women's Open.
That triumph saw her burst into the limelight, not least because of her unusual nickname of "Dumbo" and her fan club called "The Flying Dumbos" -- who would have been delighted by her magnificent play in golf's newest major.
Since its inception in 2014, Chun is the second South Korean to claim the crown, with Kim Hyo Joo winning in 2014.
She found it hard to come to terms with her triumph after a near flawless round with just a single bogey on the 14th and three birdies to maintain her overnight advantage.
