The 30-year-old Sorenstam earned the winner's share of $180,000 for her 28th career victory.
Sorenstam comments on her 5th win of 2001
'It's unbelieveable,' said Sorenstam. 'I'm a bit overwelmed. I've put in a lot of hard work, so to see the results is nice.'
Gustafson tried to reach the green from 126 yards out with a pitching wedge at the second extra hole -- the par-4 10th -- but her ball got caught up in the wind and fell short into the water. Sorenstam then knocked her approach from 113 yards to 15 feet and two-putted for the winning par.
The playoff began at the par-5 18th with Gustafson hitting her drive into the left rough. She blasted a soaring 7-iron onto the green and was left with 18 feet for eagle. She missed her first putt then tapped in to match Sorenstam, who went over the green with her second shot then chipped up and putted for birdie.
Gustafson, 27, shot a final-round 68 to finish regulation tied with Sorenstam at 13-under 203. Sorenstam birdied five of her last six holes Sunday to close with a 5-under 67 at Eagle's Landing Country Club.
Sorenstam, who started the day one shot back of third-round leaders Gustafson, Beth Daniel and Heather Daly-Donofrio, missed the first two greens Sunday and came away with back-to-back bogeys that dropped her to 6-under par.
'I was a little shaken, but I realized I've got 16 more holes and have posted low scores in the past,' said Sorenstam. 'I just needed the momentum and knew that if I could make one birdie, then I could make two, and so on.'
Sorenstam made it back to even par on the day with birdies at the third and seventh holes. Although she seemed to stall with pars over the next five holes, Sorenstam hit three approaches within eight feet for birdies at the 13th, 14th and 15th.
A 7-iron to the par-3 16th set up Sorenstam's 25-footer for birdie at the 16th. She finally took the lead with a three-foot birdie at the home hole.
Gustafson, playing behind Sorenstam in the final group, quicky fell from the lead she shared overnight after hitting in a bunker at the first hole and walking off with a double-bogey. She recouped the lost strokes with a 25-foot birdie putt at the second and a six-footer at the fourth, but dropped another shot at the fifth.
Her roller coaster round took a turn for the better with a birdie at the sixth followed by a holed wedge shot from 45 yards for an eagle at the short par-4 7th.
Gustafson continued to score on the back nine, rolling in a 20-foot birdie at the 10th and chipping to within inches for another birdie at the par-5 13th for the lead at 13-under. She bogeyed the next hole after plugging her approach in a bunker, but was able to force the playoff with a two-putt for birdie at No. 18.
'It was exciting. It's too bad I wasn't able to go all the way,' said Gustafson, who fell to 0-2 in playoffs.
Sorenstam, who defeated Mi Hyun Kim in a playoff for her fourth consecutive win of the season at The Office Depot three weeks ago, ran her record in extra holes to an impressive 10-3.
Dottie Pepper, who won this event in its inaugural year of 1992, fired a tournament-low 64 for a share of third place at 12-under with Daniel, who had a chance to join the playoff with a long eagle putt at No. 18 but birdied instead.
Scotland's Catriona Matthew, who notched her breakthrough win at the Hawaiian Ladies Open in February, carded a 69 to finish alone in fifth at 11-under, while Kelly Robbins finished alongside first-round co-leader Sara Sanders at minus-10.
Full-field scores from the Chick-fil-A Charity Championship