DALLAS, May 5, 2014 (AFP) - Lewis notched her ninth LPGA tour title but her first since the Women's British Open last August.
Her 16-under par total of 268 gave her an emphatic victory over South Korean Meena Lee, who had shared the overnight lead with Lewis.
Lee carded a one-under par 70 for sole possession of second place on 274.
American Michelle Wie was third after a 67 for 275.
South Korea's Choi Na-Yeon (69) and American Kim Kaufman (70) shared fourth on 276.
With the win, Lewis is projected to move up from her current number three in the world rankings to second in the world -- supplanting New Zealand teenager Lydia Ko.
The American had been knocking on the door, with six runner-up finishes in her previous 16 tournaments.
"It's awesome," said Lewis, a Texas native who celebrated with friends and family. "It's relief more than anything. I've been so close the last few months, you know, maybe if I win one of those, I don't get it done here. So I think it was all meant to be. Just to be here with my family."
Lewis's round included a 25-foot eagle putt at the par-five seventh hole, which she said "really kind of got things going in the right direction".
"Then I just never let up," Lewis said.
Lewis made her only bogey of the day on the par-three 11th but responded with a birdie at 12. She saved par at 15 after hitting her tee shot into the hazard.
"Making par on 15 was huge," said Lewis, who stuck her third shot there three feet from the pin. "After hitting what I thought was a good tee shot and then, you know, going in the water, but still making par, I mean that just kind of summarized the day."
Lewis capped her day with back-to-back birdies at 17 and 18 to stretch her impressive margin of victory -- the largest on the LPGA Tour since South Korean Shin Jiyai's nine-stroke victory at the 2012 Women's British Open.
"I've been wanting to do this for a long time," Lewis said. "I kind of have these mini-goals in the back of my mind, like a bogey-free tournament or a certain number of putts, just kind of things that aren't necessarily score related.
"So one of them was kind of taking a tournament and running away with it, and that's what I've wanted to do it now for a year. Just to do it here at home, in front of all these fans was pretty cool."
Leading scores after Sunday's final round of the $1.3 million LPGA North Texas Shootout (USA unless noted, par-71):
268 - Stacy Lewis 71-64-69-64
274 - Meena Lee (KOR) 70-64-70-70
275 - Michelle Wie 67-73-68-67
276 - Choi Na-Yeon (KOR) 72-69-66-69, Kim Kaufman 72-66-68-70
277 - Dewi Claire Schreefel (NED) 71-66-72-68, Lexi Thompson 70-71-67-69, Cristie Kerr 67-70-69-71, Christina Kim 67-69-70-71, Dori Carter 67-70-68-72, Suzann Pettersen (NOR) 66-71-68-72
278 - Jennifer Johnson 71-70-65-72, Jenny Shin (KOR) 69-69-68-72
279 - Amy Anderson 71-72-67-69, Chella Choi (KOR) 69-74-67-69, Alena Sharp (CAN) 73-70-66-70, Pat Hurst 72-70-67-70, Park In-Bee (KOR) 71-68-68-72
280 - Megan Grehan 76-67-69-68, Stacey Keating (AUS) 71-71-69-69, Pornanong Phatlum (THA) 70-68-71-71, Thidapa Suwannapura (THA) 70-68-68-74, Natalie Gulbis 70-65-71-74, Julieta Granada (PAR) 71-66-68-75
281 - Sarah Jane Smith (AUS) 72-70-70-69, Oh Ji-Young (KOR) 73-67-71-70, Mina Harigae 74-68-68-71, Karine Icher (FRA) 73-69-68-71, Tiffany Joh 74-66-70-71