SINGAPORE, March 3, 2013 (AFP) - Lewis, the two-day leader, was locked in a three-way tie with Choi Na-Yeon and Paula Creamer when she unleashed a blistering hybrid shot from the fairway on the the par-five seventh, landing just inches from the hole.
The tap-in eagle gave Lewis the outright lead ahead of Choi, the world number two, and whiplash victim Creamer, and despite bogeys on 15 and 17 in a gripping close she held on for her sixth career win.
"That was probably the best shot I ever hit," Lewis said of her near-albatross on seven. But she admitted she was pushed to the limit over the final holes.
"That was so nerve-wracking," said the world number four. "This golf course is so hard and then you had the pressure. Paula and Na-Yeon were just so good today."
Lewis, who spent most of her teenage years in a back brace to correct a curve in her spine, carded one-under-par 71 on a cloudy day at par-72 Sentosa Golf Club for an aggregate score of 15-under 273.
Choi finished with 72 for 274 while Creamer, also playing the final group and still feeling whiplash injuries after a car crash last Sunday in Thailand, carded 71 to finish a shot further back in third.
Thai sensation Ariya Jutanugarn, 17, cruelly robbed of victory last week by a triple bogey on the final hole, signed for 71 to finish fourth, five strokes off the winner, with Candie Kung, Jessica Korda and Danielle Kang sharing fifth.
World number one Tseng Yani showed her disgust at her closing score of 74, to wind up 13 off the lead on two-under-par 286, by tossing her ball into the lake after holing out on 18.
However Tseng, who is clinging to a rapidly diminishing lead in the standings after 107 weeks at the top, and has not won for nearly a year, said she still had plenty of time to find form this season.
"It's only three tournaments. You don't compare it with the last couple of years, that would be different," she said. "I know it's disappointing but it's the start of the season, I still have 20-something tournaments. I can still win."
Lewis, who shared the overnight lead with Choi, got off to a quiet start but she roared into outright first position with her outrageous eagle on seven.
With spectators lining the course, Lewis flirted with disaster when she landed on the drink on the par-four 15th -- but Creamer also bogeyed as her fellow American remained two shots clear.
Nerves fluttered again on 17 when Lewis bunkered and then missed a long par putt, reducing her lead to just one shot over Choi, with Creamer another stroke adrift after bogeying 16.
But Lewis powered on to the par-five 18th green in two shots, and rolled a huge eagle putt to eight feet. And when Choi missed her birdie attempt the American had two shots to win, clinching it on the second from two feet.
Leading final scores on Sunday after the HSBC Women's Champions at Singapore's Sentosa Golf Club (par 72):
273 - Stacy Lewis (USA) 67-66-69-71
274 - Choi Na-Yeon (KOR) 69-66-67-72
275 - Paula Creamer (USA) 68-67-69-71
278 - Ariya Jutanugarn (THA) 69-66-72-71
279 - Candie Kung (TPE) 69-71-69-70, Jessica Korda (USA) 72-68-68-71, Danielle Kang (USA) 68-69-70-72
280 - Lexi Thompson (USA) 73-68-69-70, Chella Choi (KOR) 68-67-74-71
281 - Catriona Matthew (SCO) 70-69-72-70, Morgan Pressel (USA) 70-71-69-71, Pornanong Phatlum (THA) 67-71-72-71
282 - Lizette Salas (USA) 67-74-70-71
283 - Jenny Shin (KOR) 71-72-70-70, Moriya Jutanugarn (THA) 73-68-71-71, Nicole Castrale (USA) 69-71-69-74, Yoo Sun-Young (KOR) 67-68-72-76
Selected
286 - Tseng Yani (TPE) 68-73-71-74
292 - Michelle Wie (USA) 71-75-77-69