Sorenstam becomes the fourth golfer to repeat as champion here. Juli Inkster did so in 1999-2000, Patty Sheehan turned the trick in 1983-1984, as did Mickey Wright in 1960-1961.
'This one feels really special. I played really well early this morning,' said Sorenstam, who has now won 12 of her last 13 events when holding the 36-hole lead, including the last eight in a row. 'For some reason it started to slip away and I felt calm, but things just stopped going my way. Obviously, I'm very glad I turned it around and it feels wonderful now.'
Sorenstam, who is also the reigning Women's British Open champion, has a chance to become the first golfer, male or female, to defend two separate major championship titles in the same season.
She finished three strokes clear of tour rookie Shi Hyun Ahn. Ahn closed with a 5-under 66 to end the tournament at 10-under-par 274.
Grace Park, who won the season's first major, the Kraft Nabisco Championship, and had lost to Sorenstam in a playoff here last year, closed with a 3-under 68 to finish at 8-under-par 276. Gloria Park and Angela Stanford, who will defend her title at the ShopRite LPGA Classic next week, ended two strokes further back at minus-6.
The field played the final 36 holes on Sunday after Friday's action was completely washed out by rain.
Sorenstam, who set a new 54-hole scoring record of 14-under-par 199, entered the final round with a commanding six-stroke lead. The Swede birdied the first hole at DuPont Country Club to extend her lead.
From there, Sorenstam looked like she might let things get away from her. She bogeyed the second and dropped another stroke at the fifth to slip to minus-13.
The 33-year-old came back with a birdie at the eighth. However, Sorenstam missed the green at the par-5 ninth with her third shot. She left her first chip short, then finally knocked her fifth shot onto the putting surface. She two-putted for a double bogey to make the turn at 12 under.
Sorenstam's slide continued as she bogeyed the 10th and 11th to fall to minus-10, where her lead was three.
'I didn't do that on purpose, but it really got exciting,' said Sorenstam, who earned $240,000 for the win. 'I told my caddie I felt calm. I felt real good, but it just didn't happen. I either selected the wrong club or I made a poor putt or missed a tee shot. It was just something on every hole.'
After Ahn got within two shots at minus-8, Sorenstam returned to form. She picked up birdies at the 12th and 14th to get back to 12 under, three shots clear of Ahn.
Sorenstam was not done either. She pulled her drive left at the par-5 16th and punched her second shot into the adjoining 11th fairway. From just under 100 yards, Sorenstam dropped her sand-wedge on the green and spun the ball within 3 feet of the cup.
She sank that birdie try and came right back with an 8-foot birdie putt at the very next hole. Sorenstam knocked her second shot into a greenside bunker at the last.
Sorenstam blasted out, but missed her par saving putt. She tapped in for bogey to close just her first over par final round to win a major championship in her career. The win was No. 52 and major title No. 7 in Sorenstam's Hall of Fame career.
'My goal was the grand slam, I didn't do that, but at least I got the second one,' Sorenstam said. 'I thought I played some really good golf this week and I was patient. It makes me feel good that I was able to turn it around when things really didn't go my way.'
Ahn, who won the CJ Nine Bridges Classic last fall, birdied the third to get to 6 under. She picked up her fourth birdie in four tries on the par-5 ninth before birdieing the par-5 11th.
The Korean kept the pressure on Sorenstam with back-to-back birdies from the par-4 15th to get to 10 under. She could only par the final two holes to finish second in just her second major championship event.
'I've never played 36 holes before, so I was kind of worried that,' said Ahn through an interpreter. 'You know it's going to be hard, boring and tiring, but as I was playing, I felt good and my shots were good. So I had a good time and enjoyed the game. My main determination was to catch Annika.'
Inkster, who played with Sorenstam for the final two rounds, stumbled to a 2-over 73 in the final round to end at 5-under-par 279. She was joined there by Christina Kim, who closed with a 72 for her best finish in a major.
Lorena Ochoa, the 2003 LPGA Tour Rookie of the Year, faltered to a 4-over 75 to end at 4-under-par 280. She was joined there by Wendy Doolan and Soo-Yun Kang. Carin Koch and Reilley Rankin, a rookie, ended one stoke further back at minus-3.