Sorenstam, five shots ahead overnight, fired a final round 73 to finish on 11-under-par at the Bulle Rock Golf Course, three shots ahead of 15-year-old American amateur Michelle Wie.
It was the Swede's ninth career major, her sixth title of the year and her 62nd LPGA victory in 11 years on the Tour.
Most importantly in her eyes, it was two out of two in the majors this year and the Swede now has her sights on becoming the first player to win all four for a season's grand slam.
Sorenstam's victory was more comfortable than the margin suggests but it was still a glorious day for Wie, whose 69 left her on eight-under with a third top 10 placing in six majors.
Another talented American teenager, 18-year-old Paula Creamer, who has already won as a rookie on the LPGA Tour, shared third place with Britain's Laura Davies on six under after a joint best of day round of 67.
Sorenstam had extended her overnight lead to eight after four holes before making four bogeys, including at the last two holes, in a back nine of 39 though by then it did not matter.
She won the first major of the year, the Kraft Nabisco Championship, by eight shots and the last two to complete a grand slam are the U.S. Women's Open at Cherry Hills in Colorado (June 23-26) and the Women's British Open (July 28-31).
