Pettersen, the leader after the second and third rounds at Ko Olina, bogeyed the final hole of regulation to set up the playoff on the par-4 18th. The 32-year-old Norwegian closed with a 5-under 67, and Salas had a tournament-record 62 to finish at 19-under 269.
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Salas had a double bogey on the playoff hole. She played a nine-hole stretch in 9 under, birdieing Nos. 8-9, holing out from the fairway for eagle on the par-4 10th and adding birdies on Nos. 12-16.
The 23-year-old American was coming off a devastating collapse two weeks ago in the Kraft Nabisco Championship when she closed with a 79 to tie for 25th after beginning the final round three strokes behind playing partner and eventual winner Inbee Park.
Pettersen won her 11th LPGA Tour title. She had consecutive LPGA Tour victories late last season in South Korea and Taiwan and won a Ladies European Tour event last month in China.
Pettersen birdied the par-3 12th get to 18 under, three strokes ahead of Salas, then bogeyed the par-5 13th after she lost her ball on her drive when she was distracted by a car honk. She birdied Nos. 14, 15 and 17 to reach 20 under, but couldn't get up and down for par on 18.
Salas has four top-10 finishes in seven starts this year. The daughter of Mexican immigrants, she was introduced to the game when her father, the head mechanic at Azusa Greens Golf Course west of Los Angeles, did some handyman jobs for the club pro and, instead of pay, asked him to teach his daughter to play. She went on to star at the University of Southern California, where she was a four-time All-America selection and helped the Trojans win the 2008 NCAA title.
Ariya Jutanugarn, the 17-year-old from Thailand, shot a 66 to finish third at 15 under.
The top-ranked Park had a 67 to tie for fourth with I.K. Kim at 13 under. Kim shot 65.
Lydia Ko, the 15-year-old New Zealand amateur who won the Canadian Open in August to become the youngest LPGA Tour winner, tied for ninth at 10 under after a 6. The South Korea-born Ko has two other pro victories, the New South Wales Open last year and New Zealand Women's Open this year, and won the U.S. Women's Amateur last season.
Second-ranked Stacy Lewis also finished at 10 under after a 71.
Local favorite Michelle Wie shot a 68, her best round of the tournament, to finish at 5 under. She broke 70 for second straight day and for only the third time in 22 rounds this season.