Park Sung-hyun is headed back to the world number one spot after a birdie at the first playoff hole lifted her to a US LPGA victory over Lizette Salas in Indianapolis on Sunday.
South Korean Park's third victory of the season sees her vault from fourth in the rankings to supplant Thailand's Ariya Jutanugarn at the top.
Ariya, who needed a top-five finish to stay at the summit if Park won, finished tied for seventh.
Both Park and Salas finished 72 holes at the Brickyard Crossing Golf Course on 23-under par 265.
Salas started the day with a two-shot lead and was up by one until a bogey at the 17th. The American still had a chance to close out the victory in regulation but missed a birdie attempt at the 72nd hole.
She carded a final-round 70 while Park, who also had a chance to seal the win at the last hole in regulation, posted a 68.
South Korean Amy Yang was third after a 69 for 266, and South Korean Ko Jin-young was fourth, posting a 67 for 268.
Both Park and Salas were in the fairway at the first playoff hole, the par-four 18th.
Salas landed her approach at the front right of the green. She made a good effort with her birdie putt, but it slipped by to open the door for Park, who rattled in a 10-footer for the win.
"I'm very honored to be ranked number one and I hope to maintain that ranking for a long time," said Park, who held the top spot for one week in November 2017. "I will try my best."
For Salas, it was a fifth runner-up finish on the LPGA tour, to go with one career victory.
"I'm just really proud of myself for keeping patient and staying focused," said Salas. "After hitting in the rough on 18 in regulation I could have freaked out, I could have done a lot of other things, but I stayed patient and I hit the shot I wanted.
"All I could ask for is an opportunity. It didn't drop, so just got to go back to work."