PITTSFORD, June 10, 2013 (AFP) - The sudden-death playoff made a long day even longer, coming after the field completed 36 holes in a marathon finish made necessary after rain washed out play on Thursday.
After both players parred the first two playoff holes -- the 18th and 10th -- they returned again to 18 -- the same hole that Park bogeyed in regulation to fall into a tie with Matthew on five-under 283.
Needing only a par to win after Matthew hit her tee shot into the rough, Park sealed her fourth win of the season with a birdie.
Park had seized the lead on Sunday morning with a third-round 68 that left her one stroke in front of American Morgan Pressel.
But the South Korean star, who won the first women's major of the year, the Kraft Nabisco Championship, in April, struggled to a three-over 75 in the final round as Matthew followed up her third-round 73 with a bogey-free 68.
Matthew came from seven strokes back going into the final round to get into the playoff -- and Park said she was fortunate she didn't give the title away in regulation.
"I actually thought I was very lucky to get in the playoff," said Park, who made three of her five final-round bogeys in the last five holes. "I just hit it everywhere. I wasn't hitting any fairways.
"I finally hit three fairways in the playoff," said Park, who added a third major title to a resume that also includes the 2008 US Women's Open.
In years past, Park would have been halfway to a grand slam, but this year the LPGA has designated the Evian Championship in France in September as a fifth major.
However, she did became just the third player to win both the Kraft Nabisco and LPGA Championship in the same season, along with Pat Bradley in 1986 and Annika Sorenstam in 2005.
"Good thing I didn't think about that," said Park, who added that she just tried to stay calm and not get angry about her wayward shots.
She became the second South Korean to win the event, after three-time winner Pak Se-Ri.
Pressel, who had led after Saturday's second round, finished tied for third on four-under 284 after rounds of 71 and 75 on Sunday.
She was joined by Norway's Suzann Pettersen, who followed up a morning 74 with a sizzling 65 to reach four-under.
Defending champion Feng Shanshan, whose victory at Locust Hill last year made her China's first major golf champion, carded a third-round 72 and final-round 70 to share ninth place on 286.
New Zealand's 16-year-old amateur prodigy Lydia Ko carded rounds of 73 and 69 on Sunday to finish on one-over 289 in a share of 17th place.
A 25-minute break separated the third and fourth rounds for the leaders.
Park stretched her lead with a birdie at the par-three fifth, but bogeyed the sixth and eighth. Pressel birdied the par-five eighth, despite hitting a tree with her second shot, and seized a share of the lead.
Pressel's challenge faced with bogeys at 10 and 12. Park appeared to be on her way after a birdie at 11 and led by three with six holes remaining.
After bogeys at 14 and 16, Park still arrived at the final hole of regulation one stroke in front of clubhouse leader Matthew.
"When I started today the last round I probably didn't realize I could win," Matthew said. "So to play well and get into the playoffs was obviously pretty good. "Obviously when you get into it, it's pretty disappointing (to lose), but a overall pretty good week."
Leading final-round scores here on Sunday in the LPGA Championship (x-won playoff; a-amateur; USA unless noted; par-72):
283 - x-Park In-Bee (KOR) 72-68-68-75, Catriona Matthew (SCO) 71-71-73-68
284 - Suzann Pettersen (NOR) 72-73-74-65, Morgan Pressel 68-70-71-75
285 - Yoo Sun-Young (KOR) 73-69-70-73, Amy Yang (KOR) 71-70-74-70, Shin Jiyai (KOR) 68-73-69-75, Chella Choi (KOR) 67-73-73-72
286 - Feng Shanshan (CHN) 74-70-72-70, Michelle Wie 76-68-71-71, Choi Na-Yeon (KOR) 72-70-70-74
287 - Anna Nordqvist (SWE) 71-74-73-69, Cristie Kerr 75-72-70-70, Caroline Masson (GER) 74-69-71-73
288 - Ai Miyazato (JPN) 74-75-66-73, Kristy McPherson 73-72-69-74
289 - a-Lydia Ko (NZL) 77-70-73-69, Brittany Lincicome 69-73-77-70
290 - Beatriz Recari (ESP) 74-71-73-72, Jennifer Rosales (PHI) 76-71-70-73, Tseng Ya-ni (TPE) 72-74-71-73
291 - I.K. Kim (KOR) 75-74-73-69, Mina Harigae 75-74-73-69, Mika Miyazato (JPN) 77-71-71-72, Danielle Kang 75-72-72-72, Jenny Shin (KOR) 78-70-70-73, Ji Eun-Hee (KOR) 72-72-74-73
292 - Stacy Lewis 74-72-76-70, Pak Se-Ri (KOR) 70-74-76-72, Lexi Thompson 71-73-73-75, Angela Stanford 71-71-75-75, Pernilla Lindberg (SWE) 73-71-71-77