Gaby Lopez won her first LPGA Tour event with a one-over-par 73 to finish one shot ahead of world No.1 Ariya Jutanugarn in the Blue Bay tournament in China.
Playing in a group with Mexican world No.136 Lopez, No.1-ranked Jutanugarn of Thailand had a birdie on the final hole to also finish on 73 on Hainan Island. The final event of the LPGA season, the CME Group Tour Championship with a prize of $1 million for the victor, will be held in Florida next weekend.
López had marked her 25th birthday on Friday by hitting a hole-in-one at the 17th, grabbing the third-round lead.
Celine Boutier shot a 66 and finished two shots off the lead. She finished at 8-under 280.
Lopez, an alumnus of the University of Arkansas golf programme, was the second first-time victor on the LPGA's Asian swing after Nelly Korda claimed her maiden title in Taiwan two weeks ago. "That's why I'm actually a professional golfer".
Lopez is the first victor from Mexico since Lorena Ochoa, a driving force for the game in that Latin American country.
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Jutanugarn though would fight her way back into the event with a back nine of 33 and Lopez felt the pinch with bogeys at her final two holes to just hold on.
Lopez said she was also thinking of her grandfather, Jose Lopez, who died recently.
"I always told him that I was going to give him my first trophy", Lopez said.
"She did a great job last two days", Jutanugarn said, knowing Lopez was "nervous sometimes".
Australia's Hannah Green and Sarah Jane Smith finished in a three-way tie for 15th at three over for the event.
The Blue Bay tournament wraps up five straight weeks of play for the top women's golf tour in Asia.