San Francisco - Brittany Lang won the US Women's Open on Sunday in a three-hole playoff over Anna Nordqvist, whose challenge was doomed by a two-stroke penalty at the second playoff hole.
Nordqvist was penalised for grounding her club in a fairway bunker, with video showing her club barely touching the sand before she hit out.
That paved the way for Lang - who parred all three playoff holes - to capture her first major title at CordeValle in San Martin, California.
The two had ended regulation tied on six-under par 282 - two shots in front of a group that included world number one Lydia Ko.
America's Lang, who captured her only prior LPGA Tour title at the 2012 Manulife Financial LPGA Classic, closed with a one-under 71.
"I can't believe it. It means absolutely everything," said Lang, 30. "This is what you dream of. It's amazing."
Lang had taken sole possession of the lead at the par-three 16th, where she rolled in a 15-foot downhill birdie putt.
But a three-putt bogey at 17 dropped her back into a tie for the lead with Nordqvist.
Nordqvist, who had stormed to the top of the leaderboard with a final-round 67 that included three birdies and an eagle, didn't learn of the penalty until after her third shot at the final playoff hole.
"Well, first, I couldn't really believe that it happened," said Nordqvist. "It wasn't my intention to ground the club... probably misjudged it a little bit and touched a little bit of sand and that is a penalty. I just wish they would have told me a little earlier."
Nordqvist said she might have been a little more aggressive with her shot into the green if she'd known she was two strokes adrift.
"It might not have changed anything, but I just wish it was a little bit earlier."
The US Golf Association's timing in telling the players of Nordqvist's penalty recalled the rules fracas at the men's US Open, where the USGA came in for criticism of its handling of a penalty assessed eventual winner Dustin Johnson -- who was told by on-course officials he wouldn't be penalized after his ball moved on a green, then told he might be, then finally was.
While Nordqvist wished she'd learned sooner of the penalty, she had no argument with the decision.
"Hey, I made a mistake and I will have to take the consequences for it," she said.
Lang sympathised with Nordqvist, acknowledging that knowing she had a cushion made things easier for her as she hit into the final playoff hole.
"Definitely it took a little bit of pressure off me," she said.
Ko, seeking at 19 to become the youngest golfer to win a third major title, led after three rounds and had stretched her advantage to two strokes with a birdie at the sixth.
But the New Zealander followed a bogey at the eighth with a double-bogey at the ninth.
"When you're doubling a par-five, it doesn't help the scorecard," acknowledged Ko, who had two more bogeys and a birdie coming in.
South Korea's Park Sung-Hyun, who led after 36 holes, bogeyed the last to complete a 74 that left her tied for third on 284 alongside Ko and South Koreans Amy Yang (73) and Ji Eun-Hee (74).
Leading final-round scores on Sunday in the US Women's Open at CordeValle in San Martin, California (x-won in three-hole aggregate playoff; par-72, USA unless stated):
282 - x-Brittany Lang 68-75-68-71, Anna Nordqvist (SWE) 68-74-73-67
284 - Amy Yang (KOR) 67-71-73-73, Ji Eun-Hee (KOR) 69-71-70-74, Lydia Ko (NZL) 73-66-70-75, Park Sung-Hyun (KOR) 70-66-74-74
285 - Stacy Lewis 71-74-69-71
286 - Jodi Ewart Shadoff (ENG) 70-71-75-70, Gerina Piller 70-72-74-70, Cristie Kerr 67-75-72-72
287 - Ryu So-Yeon (KOR) 71-76-71-69, Sydnee Michaels 69-72-75-71, Lee Mi-Rim (KOR) 64-74-76-73, Haru Nomura (JPN) 70-69-75-73, Gaby Lopez (MEX) 71-72-71-73, Angela Stanford 71-70-71-75
288 - Lee Lopez 73-72-71-72, Jessica Korda 70-70-75-73, Ariya Jutanugarn (THA) 70-75-69-74, Danielle Kang 71-69-73-75
289 - Jang Ha-Na (KOR) 73-71-74-71, Suzann Pettersen (NOR) 72-74-72-71, Mo Martin 71-70-77-71, Alena Sharp (CAN) 70-72-75-72, Kris Tamulis 71-72-71-75
290 - Christina Kim 70-75-73-72, Maude Leblanc (CAN) 72-69-76-73, Lin Xiyu (CHN) 73-73-73-71, Lizette Salas 70-78-71-71, Catriona Matthew (SCO) 73-72-71-74, Kim Sei-Young (KOR) 75-68-72-75