Karrie Webb fired a sensational course-record 63 to win the JTBC Founders Cup in Phoenix.
The Australian, who went into the final round six shots behind overnight leader Lydia Ko, had to wait for an hour and a half after her brilliant nine-under round to see if anyone could beat her.
No-one could, Ko and four others finishing a shot behind, and the 39-year-old clinched her second LPGA Tour victory of the season and second in four years at Desert Ridge.
Webb carded 10 birdies and a bogey, playing the back nine in six-under 30. She birdied five of the last six holes, finishing with a 20-footer on the par-four 18th.
Webb won the Women's Australian Open for a record fifth time last month and now has 41 LPGA Tour victories.
Ko, the teenage sensation from New Zealand, parred the final three holes to finish a stroke back, along with 2013 winner Stacy Lewis, Azahara Munoz, Amy Yang and Mirim Lee.
Ko, 16, finished with a 70. She led by three strokes after birdieing the second, third, fourth and fifth holes, but slipped back with bogeys on six, nine and eleven.
Munoz and Yang, playing together in the third-to-last group, missed long birdie putts on 18 and each shot 67. Lee shot 69 in the next group, also missing a long birdie try.
That left Ko as the only player who could potentially top Webb. Her 25-foot try on the last hole was just short and right.
Lewis birdied the final two holes for a 66.