Brooke Henderson birdied the last to win the Evian Championship by one shot and lift her second major title.
The Canadian, 24, claimed her first major in the 2016 Women’s PGA Championship.
Henderson finished on 17-under, edging Sophia Schubert, and said: “I’m super excited to have my second major win.”
England’s Charley Hull ended on 15-under and tied third in a group of five golfers, while compatriot Georgia Hall was two shots back and tied for eighth.
Henderson, who struggled to a 71 in the last round, had to battle for the victory.
She had lost her lead, but bounced back with back-to-back birdies on 14 and 15, before rolling in the decisive eight-foot putt to triumph.
“It was definitely an interesting day. Not the day I wanted but I stayed patient,” added Henderson.
“The saying is majors are won on the back nine on Sunday, so I kept that in mind.”
She added time spent with family has also helped her game.
“I took a break a couple of months ago and went home and spent time with my mum and dad – he’s my coach – and my [caddie] sister, Brittany also helped me work on a few things in my game,” said Henderson.
“I came back and won a tournament last month [ShopRite LPGA Classic] and now this. I feel I’ve got a really good mindset and now I’m just hoping to continue with the same form.”
Schubert, a former US Women’s Amateur champion, took second place as an LGPA rookie – and the 26-year-old wants to carry the momentum with her.
“I was just trying to stay calm coming down the stretch and didn’t know until the last hole where I stood,” she said. “I decided not to look at the leaderboards.
“It was not to be, but I’m very happy with my effort and I just want to carry the momentum through the rest of the season.”
Japan’s Mao Saigo hit a stunning seven-under-par 64 in round four to join Hull in third place.
Having started six shots adrift, Hull moved up the leaderboard with a 67 and said: “I’ve had quite a good start to the season.
“Just feel good going into the Scottish and British [AIG Women’s Open]. Back in contention, especially in a major.”