'It's always great to come back to a tournament where I've done well in the past,' said Sorenstam, who picked up $262,500 for her third win here. 'I'm very excited right now and very happy to finish the way I did.'
Sorenstam became the third youngest player to reach the 50-win mark on the LPGA Tour. She also defended a title for the 11th time on the LPGA Tour.
'Fifty is kind of a magical number,' Sorenstam said. 'I've thought about this for a little while. This is why I practice and why I'm here. I love to win.'
Ashli Bunch fired a course-record 7-under 65 in the final round to finish at 6-under-par 210. She was tied there by Meg Mallon, who closed with a 70. Bunch was later joined as course record holder by Isabelle Beisiegel, who also closed with a 65 to end at even-par 216.
Sorenstam, who also won here in 2001 and 2003, opened with four straight pars at El Caballero Country Club. She then dropped in a birdie putt at the par-4 fifth to move to 7 under.
The Swede stumbled to a bogey at the very next hole, however. She then ran off seven consecutive pars around the turn, while her opponents were making a charge.
Bunch, playing six groups ahead of the leader, ran off three straight birdies from the 10th to get to minus-4 and within two strokes of Sorenstam, the closest anyone was since Rosie Jones and Mallon started at minus-4.
Bunch settled down to par four consecutive holes. She then knocked a fairway wood within three feet to setup eagle at the par-5 17th and tie Sorenstam in the lead at 6 under. However, she missed a short birdie try at the last.
'When I was playing the 12th hole, I looked over and saw that Ashli hit it to one foot or so for eagle at the 17th,' said Sorenstam. 'That's when I started to feel the pressure and I just told myself to hang in there and be patient.'
Sorenstam knowing she had been tied for the lead turned it on. The top player in the women's game dropped her second shot to the par-4 14th within eight feet. She calmly rolled in the putt to regain the lead.
After a two-putt par at No. 15, Sorenstam rolled home an 8-foot birdie at the very next hole to open up a two-shot lead.
Sorenstam was not finished either. She two-putted for birdie at the par-5 17th, before a casual two-putt par at the last gave her the seventh wire-to-wire victory of her career. She now has won four different tournaments three times.
'I still have a hard time believing it's 50 wins,' said Sorenstam, who also won the Samsung World Championship, Mizuno Classic and Michelob Light Classic three times. 'Like I said, it's a magical number. I guess I try not to think too much about it because it gets me a little sentimental. But I thought I worked really hard this week, and it feels really, really good to win here.'
Bunch, who picked up two birdies on the front nine, used her back nine run to secure her best ever finish on the LPGA Tour. She could have pushed Sorenstam further but missed short birdie tries at Nos. 14 and 15. Bunch's best previous finish was a tie for fourth at the 1999 Welch's/Circle K Championship.
'To be honest, I didn't tee it up thinking I could win the tournament,' said Bunch. 'I knew I could pass a lot of people, but my husband Michael (who is also her caddie) said last night that Annika is going to be tough to beat.'
Mallon had a rough start with a double bogey at the second and back-to-back bogeys from the third. She rebounded with birdies at the seventh and eighth. She then birdied the 11th, but dropped a shot at the 12th.
Mallon closed out in excellent fashion as she birdied four of the final five holes to climb back to minus-6 and a share of second place.
Lorie Kane also broke the previous course record as she posted a 5-under 67 to share fourth place at 4-under-par 212. She was joined there by Mi Hyun Kim, who posted a 69.
Tina Barrett and Catriona Matthew shared sixth place at 2-under-par 214, with Michelle Ellis, Lorena Ochoa and Michele Redman finishing one stroke further back at minus-1.
Beisiegel was joined at even par by Hall of Famer Betsy King, who closed with a 1-over 73.