South Korean So Yeon Ryu birdied the first extra play-off hole to claim a dramatic victory over Lexi Thompson in an incident-packed final round at the ANA Inspiration held at Mission Hills Country Club in California.
Ryu rolled in a six-foot birdie at the 18th in the play-off to edge ahead of Thompson, who was controversially handed a four-stroke penalty mid-round for an incident from the previous day.
The pair had finished level on 14 under for the tournament, with Inbee Park and Minjee Lee a further stroke back alongside Suzann Pettersen.
Taking a two-shot lead in to the final round, Thompson extended her advantage with three birdies in his opening seven holes, but carded a first bogey of the day at the par-four 12th.
It was at that point the American was punished by tournament officials for incorrectly replacing a marked ball on the 17th green on Saturday, while also incorrectly signing her scorecard. Each infringement cost her two shots.
After being told of the penalty, Thompson teed off at the 13th hole in tears, but battled back bravely with a long-range birdie to retain a share of the lead, before cancelling out a birdie at the 15th with a bogey-five at the next.
Trailing clubhouse leader Ryu by one as she headed to 18th, Thompson found the par-five green in two, but left her 15-foot eagle putt for victory just short to close with a five-under 67. Ryu then birdied the first playoff hole to win the title.
“I cannot believe the situation,” said Ryu, for whom this was her second major title. “I didn’t even check the leaderboard, Lexi was playing so well. I didn’t expect it.”
Further down the leaderboard, defending champion Lydia Ko finished tied 11th, while England’s Charley Hull claimed a share of 14th.