World No 3 Lydia Ko held her nerve in the face of a strong challenge from Danielle Kang on Sunday, firing a three-under par 67 to win the LPGA at Boca Rio by one stroke.
New Zealand's Ko started the day with a two-shot lead over America's Kang, who was trying to go back-to-back after winning the LPGA Tournament of champions in Orlando last week.
Kang gained ground quickly with birdies at the first and third as Ko opened with a birdie at the first and a bogey at the second at the Boca Raton, Florida, resort.
After matching birdies at the 11th, Kang edged ahead with a birdie at the 12th, but she bogeyed 13 and when Ko birdied 15 she was alone in first again.
Both birdied 16 from the same greenside bunker and arrived at 18 with Ko nursing a one-shot lead.
She found both a fairway bunker and a greenside bunker, but blasted out to a foot to save par as Kang was unable to get her mid-range birdie attempt to fall.
Although the conditions were sunny and warm compared to the blustery chill of Saturday, Ko admitted the round was "a grind."
But she got herself out of trouble when she had to, going three-for-three on sand saves on the back nine to capture her 17th LPGA title against her long-time friend with a three-under par 69 for a 14-under total of 274.
"She's obviously one of the players I've known for the longest time out here," Ko said of Kang. "She has kind of taken me under her wing.
"I just tried to focus on me and tried to play the best golf I can. At points it was a bit of a grind but I'm glad that I could get that done."
Kang closed with a 68 for 275, while Japan's Yuka Saso carded a 67 to finish in solo third on 276.
France's Celine Boutier, who played in the final group, carded a 69 for 277 and shared fourth place with England's Charley Hull, who signed for a 68.
Ko, who won her first LPGA title at the age of 15, rose to No 1 in the world, then struggled through a near three-year title drought.
But Ko won in Hawaii last year and said she feels she has turned a corner.
"I think last year was kind of a big turnaround year for me and even the fall of 2020," said the 24-year-old, who also won bronze at the Tokyo Olympics last year.
"When we had that long time off it was a time for me to look back at what are the things I need to work on and just take a whole new approach to things.
"I feel like it has been much more consistent. Last year, even though I didn't win on the LPGA at the end of the year, I put myself in contention quite a bit and when you keep knocking on the door you feel like at one point it's going to open."
FINAL ROUND SCORES
274- Lydia Ko (NZL) 63-70-72-69
275- Danielle Kang 65-68-74-68
276- Yuka Saso (JPN) 67-70-72-67
277 - Charley Hull (ENG) 67-71-71-68, Celine Boutier (FRA) 72-67-69-69
281- Lexi Thompson 70-70-73-68, Brooke Henderson (CAN) 68-71-74-68
282- Choi Hye-jin (KOR) 67-72-73-70, Maude-Aimee Leblanc (CAN) 67-72-74-69, Stacy Lewis 68-72-72-70
283- Georgia Hall (ENG) 70-70-76-67, Ally Ewing 68-73-72-70
284- Bronte Law (ENG) 68-70-78-68, Amy Yang (KOR) 68-74-73-69, Aditi Ashok (IND) 66-72-76-70, Patty Tavatanakit (THA) 71-68-74-71, Jodi Ewart Shadoff (ENG) 68-69-76-71
285- Pauline Roussin-Bouchard (FRA) 73-70-74-68, Ayaka Furue (JPN) 69-72-71-73