Hull, 28, started the third and final round two strokes behind Pia Babnik of Slovenia, but five birdies in the first seven holes pushed her into a lead she was able to hang on to as she won by three shots.
“I felt really sharp, I played very solidly,” said Hull after claiming a fourth Ladies’ European Tour victory, to add to two LPGA titles.
“I made a bogey on the par-five 17th and the par three, but that was just two three putts. [They were] quite long putts and they got away from me a little bit, but I felt like I held my game together pretty well.
“And 18 under for three days is a pretty good score.”
Hull – ranked 15th in the world – won by three shots from Denmark’s Nicole Broch Estrup, with Babnik in third after a costly round of 73.
Fatima Fernandez Cano, who had a birdie putt for a record-equalling round of 61 on Friday, followed up with a 73 to finish tied for fourth place.
Meanwhile, the third round of the LPGA’s Toto Japan Classic was cancelled on Saturday because of heavy rain caused by Typhoon Kong-rey in Shiga.
The event will be shortened to 54 holes, with the final round on Sunday. Japan’s Hana Wakimoto is in the lead on 13 under.