Paula Creamer knocked in a long birdie at the 15th to retake the lead and held on en route to a one-stroke victory at the Samsung World Championship.
It was the fourth victory of the year and eighth in the 22-year-old's career as she finished with a three-under-par 69.
The Californian's four wins this season are the most by an American player since Juli Inkster collected five in 1999.
Beyond adding to a strong campaign, it was an emotional win for Creamer, who broke down in tears during a TV interview after winning near her hometown of Mountain View.
"This means a lot. That is (a) big win for myself," she said later. "I put so much pressure on myself every time I come here and to finally have one, it feels really good. I'm very excited.
"I briefly looked at my phone and people kept saying, 'Did I see you cry? I didn't think you had emotions' and all of this. It does. It really means a lot to me, this win."
Creamer came into the final round with a one-shot lead following a 68 on Saturday. That slim edge disappeared on the back nine when Korean Kim Song-hee birdied the 14th to pull even at eight-under.
As if losing the lead was not enough, two-time defending champion and world number one Lorena Ochoa and the Hall of Famer Inkster both notched a birdie at 16 to pull within a stroke. Also moving to seven-under was Suzann Pettersen with a birdie at the 15th.
Despite the crowd at the top of the leaderboard, Creamer did not lose her focus, coming up with a birdie putt from 25 feet out on her next hole to move back ahead. She maintained that lead until the 18th, when a shaky birdie attempt nearly cost her.
However, Creamer was able to lip in a par putt to seal the win, ending up at nine-under 279.
"Honestly, I didn't see it go in," Creamer said about the clinching putt. "All I heard was the people cheer for it, then I was like, it was like the longest two seconds of my life having it roll into the hole."
Seeking her first win on the LPGA Tour, Kim finished a shot behind following a final-round 68.
It was the second time the 20-year-old was a runner-up this season, ending up 11 strokes behind Ochoa at the Corona Championship in April.
"Going in (Saturday), I didn't have a great feel for my shots, so I was a little worried coming into the round," Kim said through an interpreter. "But I played pretty well. I had a lot of opportunities but I wasn't able to convert all of them, so I'm a little frustrated."
Ochoa, who was trying to become the fourth player to win this event at least three times, ended up in a tie for third at 281 following a 69.
The Mexican finished tied with Inkster (68), Pettersen (68) and Angela Stanford (70). Ochoa had a much better showing on the back nine than she had on Saturday, notching an eagle at the par-five 10th and the birdie on 17th. However, she went into a bunker on her approach of the 18th green before having to save for a par.
She struggled mightily after the turn in the third round, ending up with a double bogey at 13 and two other bogeys en route to a one-over 73 to hamper her chances for another crown. Inkster was looking for her fourth win here, claiming her last title back in 2000.
A five-time champion here, Annika Sorenstam finished in 15th at three-over-par 291 following a closing-round 70.
Collated final round scores & totals
(USA unless stated, par 72):
279 Paula Creamer 68 74 68 69
280 Song-Hee Kim (Kor) 69 73 70 68
281 Juli Inkster 73 72 68 68, Angela Stanford 69 73 69 70, Lorena Ochoa (Mex) 69 73 70 69, Suzann Pettersen (Nor) 74 70 69 68
282 Katherine Hull (Aus) 70 73 69 70
283 Ji-Yai Shin (Kor) 67 76 70 70, Eun Hee (Kor) Ji 73 73 70 67
285 Cristie Kerr 73 73 68 71
286 Jeong Jang (Kor) 72 76 68 70
287 Seon Hwa Lee (Kor) 75 69 72 71
289 Ya-Ni Tseng (Tai) 69 74 74 72, Hee-Won Han (Kor) 75 71 72 71
291 Annika Sorenstam (Swe) 69 77 75 70
293 Karrie Webb (Aus) 74 76 73 70
294 Na Yeon Choi (Kor) 69 71 75 79, Helen Alfredsson (Swe) 75 73 76 70
296 In-Bee Park (Kor) 77 71 74 74
300 Angela Park (Bra) 76 76 75 73
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