EVIAN, September 15, 2013 (AFP) - The 32-year-old Norwegian, winner of the Safeway Classic in Oregon two weeks ago, shot a final round 68 for 10 under par 203 in a Championship that had major status for a first time but had to be reduced to 54 holes due to weather problems.
Pettersen received a cheque for 350,000 euros and finished two ahead of second place Ko, who closed with a 70 for eight under.
"It's great to win another major and this one has definitely been well worth waiting for," said Pettersen.
"I was actually really nervous coming down the stretch and even nearly played up short at the 18th (a par four over water). But I said to my caddie I had to go for it and it worked out."
New Zealand's Ko, already a four time winner alongside the professionals, was one off the lead overnight but led on her own after she nearly holed her second shot and had an easy birdie three at the opening hole.
A three-putt bogey at the short second set her back and Pettersen, a star of last month's European Solheim Cup victory, then took the lead for the first time with a key 25-foot birdie putt at the eighth.
At the long 13th, Ko drove into a bunker and then failed to get up and down from the side of the green and a Pettersen par edged the more experienced player two in front.
There was a late scare for Pettersen when she drove into trees and had to chip out sideways at the par four 17th.
But a third to four feet to save par was another killer blow.
For Ko, who refuses to divulge when she will join the paid ranks, it was another astonishing performance.
Just last month, she retained the Canadian Open.
"It has been a great week," she said.
"I didn't take all my chances but Suzann played really well."
American teenager Lexi Thompson shot 68 and was alone in third place on six under par, but South Korea's Park Inbee, the world number one and winner of the first three majors this season, had a low key championship.
Never in contention, she closed with a 76 for five over par and was outside the top 60.
Japan's Mika Miyazato, one ahead after both the first and second round, stumbled to a 79 for and a tie for 15th.
With Thursday's play having been completely wiped out, it had been decided on Friday to cut the event to 54 holes.
It had been feared that more downpours would cause havoc on Sunday, although play started two hours late due to overnight rain, they managed to complete with no further delays.
For Heather Daly-Donofrio Senior Vice-President of Tour Operations for the LPGA Tour, getting finished before dark was a real relief.
"It's a miracle we got done," she said.
Leading final round scores on Sunday at the Evian Championship USLPGA tournament (par 71; tournament reduced to 54 holes due to bad weather):
203 - Suzann Pettersen (NOR) 66 69 68
205 - Lydia Ko (NZL) 68 67 70
207 - Lexi Thompson (USA) 72 67
208 - Pak Se Ri (KOR) 66 71 71, Ryu So Yeon (KOR) 71 66 71
209 - Angela Stanford (USA) 69 71 69, Stacy Lewis (USA) 69 67 73, Choi Chella (KOR) 70 67 72
210 - Jennifer Johnson (USA) 70 70 70, Beatriz Recari (ESP) 69 69 72
211 - Feng Shanshan (CHN) 70 72 69, Lizette Salas (USA) 70 71 70, Lee Ilhee (KOR) 70 71 70, Rebecca Lee-Bentham (CAN) 75 66 70
212 - Ai Miyazato (JPN) 75 68 69, Cindy LaCrosse (USA) 73 70 69, Katherine Hull-Kirk (AUS) 71 71 70, Karrie Webb (AUS) 68 72 72, Mika Miyazato (JPN) 65 69 78
213 - Lee Mi Hyang (KOR) 73 70 70, Caroline Hedwall (SWE) 74 68 71, Sandra Gal (GER) 66 74 73, Azahara Munoz (ESP) 70 71 72, Paula Creamer (USA) 70 69 74, Kim In-Kyung (KOR) 69 69 75
214 - Ayako Uehara (JPN) 69 73 72, Han Hee-Won (KOR) 69 72 73, Holly Clyburn (GBR) 71 70 73, Mina Harigae (USA) 71 73 70, Momoko Ueda (JPN) 70 70 74
* - denotes amateur