South Korea's Haeran Ryu has staged a stunning turnaround from a third-round meltdown to win the LPGA Tour's FM Championship in a playoff at rainy TPC Boston.

Four strokes behind former world No.1 Jin Young Ko entering play on Sunday after blowing a six-stroke lead on Saturday, Ryu closed with an eight-under 64 to match Ko at 15-under 273.

She then beat her countrywoman with a par on the first hole of a playoff.

On the extra hole in fading light, Ryu hit her 120-yard third shot to 12 feet on the par-5 18th, then watched Ko fire her 111-yard approach over the back of the green. Ko chipped to about 30 feet and made bogey, with Ryu then lagging her birdie putt to a foot and tapping in for her second LPGA Tour victory.

"I was so nervous at the playoff, but maybe Jin Young Ko is same as me," Ryu said. "I think just thank for God. I can't believe it here now."

Ryu had shot a career-best 62 on Friday to take the six-stroke lead into the weekend, then had a 78 on Saturday.

"My caddie and my other teammates said to me, 'Just for today it's bad, and tomorrow it all comes through. Just trust yourself,'" Ryu said.

Ko, a 15-time LPGA Tour winner without a victory since May 2023, missed an 8-foot birdie try on 18 for the win in regulation. She shot 68.

"I played really, really good this week," Ko said. "Unfortunately, just the last shot wasn't good and I lose. But overall, I played really solid, and congrats to Hae Ran."

Ryu won the NW Arkansas Championship last year as an LPGA Tour rookie and has five victories on the Korean tour.

"Really happy because first win is so hard, but second is hard again," Ryu said.

Ruixin Liu of China was a stoke back in third place after her second straight 64, the lowest scores of her LPGA Tour career.

She birdied the first seven holes Sunday - three days after making a quadruple bogey on her opening hole of the tournament.

"I can't believe it's true because starting with a 9 off the bat, I didn't really even think I can make the cut," Liu said.

Allisen Corpuz and AJeeno Thitikul each shot 67 to tie for fourth at 13 under.

Australia's Hannah Green shot a closing 67 to tie for 10th, six shots outside the playoff, while her countrywoman Robyn Choi (70) was tied 25th at five under.