The Swede now owns nine major championship titles. This is the second year in which Sorenstam has won two majors as she won this title and the Women's British Open crown in 2003.
Sorenstam, who tied the 54-hole tournament scoring record, also became the first woman to win the same major three consecutive years.
'I'm very, very happy. This has been a great week in so many ways,' Sorenstam said. 'As you all know, I have some really lofty goals, and to come here and feel pressure, not just from myself, but from everyone, to come here and play so well for four days, I'm very happy to win and make this another victory.'
Sorenstam has now won six of her eight starts this season. Dating back to last season, she has won eight of her last 10 starts. Finally, since her appearance on the PGA Tour at the 2003 Colonial, Sorenstam has titled in 19 of her 38 starts on the LPGA Tour.
'Well, I have to be honest, I do have to pinch myself sometimes when I look at my results,' said Sorenstam, who collected $270,000 for the win. 'I mean, I feel like I'm just a little girl from Sweden that came over here to follow my dreams and hope to win a few golf tournaments. When I look at my bio in the LPGA media guide, I definitely get overwhelmed.'
Amateur sensation Michelle Wie posted a 3-under 69 to finish alone in second place at 8-under-par 280. The second-place finish marked her best major on the LPGA Tour, bettering her fourth-place finish at the 2004 Kraft Nabisco Championship.
Paula Creamer, the 18-year-old who won three weeks ago at the Sybase Classic, fired a 5-under 67 at Bulle Rock Golf Course. She shared third place at 6-under-par 282 with Laura Davies, who won this crown in 1994.
Sorenstam opened the round with a 12-foot birdie putt on the par-3 third to move seven strokes clear of the field at minus-13. She stumbled to a three-putt bogey on the sixth, but erased that error with a birdie on No. 7.
The 34-year-old ran in a 15-foot birdie try at the 10th. Sorenstam bogeyed the next, though, and her lead fell to six.
After three straight pars, Sorenstam tripped to a three-putt bogey at 15. She got that stroke back with a birdie at the next. Sorenstam did falter to bogeys on each of her last two holes to win by three. The one-over 73 snapped her run of 14 straight rounds in the 60s, an LPGA Tour record.
'I was very nervous playing today and I started off pretty good on the front nine,' Sorenstam said. 'I got a little shaky in the end, but I'm just glad it's over and that I won.'
Wie struggled to a bogey at the second, but that was the youngster's last mistake. She birdied the par-5 eighth, for the third time this week, to get back to 5 under.
The 15-year-old dropped in back-to-back birdies from the 10th to move into second place. Wie parred her next three holes before a birdie at the 15th. She closed with three pars in a row to secure second place.
'You know, I just felt really good about myself today,' said Wie. 'My energy level was back up to normal today, and if a couple putts went in the first couple of holes, it would have been a different story, but I'm totally happy how I finished.'
Creamer played a flawless round on Sunday. She posted three birdies over the front nine to move to minus-4. Around the turn, she birdied the 13th and 17th to share third place.
Davies played the front side at 1 under with a bogey and two birdies. After a birdie on 11, the Englishwoman stumbled to a double-bogey on the 12th that ended her chances. She got one stroke back with a birdie on the 15th before three straight pars to cap her round of 71.
Natalie Gulbis and Lorena Ochoa tied for fifth at 4-under-par 284. Moira Dunn, Pat Hurst, Mi Hyun Kim, Young Kim, Carin Koch and Gloria Park were one stroke further back at minus-3.