Lydia Ko secured her second LPGA tournament victory of the year by winning the Marathon Classic by one shot in Sylvania, Ohio.
Ko and Ryu So-yeon were tied on 14 under with one hole to play, but the 17-year-old New Zealander claimed victory at Highland Meadows Golf Club when she birdied the 18th to card a 15 under final-round 66 which her opponent could not match.
"I hit the ball well and gave myself a lot of opportunities," Ko said. "You have good chances when you get the ball on the green."
Ryu saw her eight-foot birdie effort at the 18th pull just right of the cup, leaving the South Korean dejected.
"Absolutely I'm disappointed I missed (that) birdie putt," she said. "Sometimes if I get something lucky, then I get something that is unlucky. I just accept it and let it go."
American Christie Kerr was third, three shots adrift of the tournament-winning total on 12 under, while Malaysia's Kelly Tan, Katherine Kirk of Australia and South Africa's overnight leader Lee-Anne Pace were joint fourth a further shot back.
England's Jodi Ewart Shadoff was the best-placed Briton, but could only manage a joint-60th place finish on one under par after a final-round 68.