Ahn posted a 2-under 69 to come in at 5-under-par 208. Candie Kung also shot 69 to end at 3-under-par 210, with Heather Bowie and Mi Hyun Kim one stroke further back at minus-2.
Sorenstam's playing partner Joanne Morley got within two strokes of the leader with birdies at the first two holes. However, Morley quickly fell off the pace with five bogeys over the final seven holes of her front nine.
Sorenstam meanwhile opened with five straight pars before dropping in a 13-foot birdie putt at the par-3 sixth at Cedar Ridge Country Club. She cruised around the turn with four pars in a row from there.
The Swede then rolled in a 28-footer for birdie at the par-4 11th to get to 10 under. Sorenstam stumbled to a bogey at the 13th, but came right back with a birdie at the 14th to get back to minus-10. She birdied the 14th all three rounds of the event.
Sorenstam, who also won here in 2002, coasted in with three pars in a row before bogeying the 18th when she was unable to get up-and-down for par.
'Anything can happen on any hole. You've got to be patient,' said Sorenstam, who won $150,000. 'I felt pretty comfortable with a three-shot lead knowing that this is a tough course to go low at.'
The win for Sorenstam was her fifth of the season on the LPGA Tour and seventh worldwide. She climbs within two wins of Betsy Rawls, who stands in fourth place on the all-time wins list.
'I thought I played excellent for three days,' said Sorenstam, whose last event was five weeks ago at the Women's British Open. 'It's a tough course. I'm just really surprised how well I hit it and putted it. To make it my 53rd here in Tulsa, when I played not so good here, it's a special week.'
The fifth win means Sorenstam has now won at least five events in each of the last five years, a feat that has been accomplished just two other times.
'I think about those things. I am surprised that I've played so well,' Sorenstam said. 'I'm very proud of my career.'
Ahn started her day with a bogey at the first, but rebounded to birdie the second. She later birdied the fifth and seventh, before stumbling to another bogey at the eighth. She capped her round with a 9-foot birdie putt at the last.
Shani Waugh closed with a 2-under 69 to join Kelli Kuehne (72) at 1-under-par 212 in a tie for sixth. Laura Diaz, Candy Hannemann, Morley and Karen Stupples were one stroke further back at even-par 213.
Karrie Webb, the 2003 champion, posted a final-round 72 to end at 2-over-par 215 in a tie for 17th.