Ai Miyazato suffered a final-round meltdown and finished tied for 18th as New Zealand's world No. 1 Lydia Ko became the youngest two-time major champion with victory at the ANA Inspiration on Sunday.

Miyazato started the day in title contention two strokes off the pace in a tie for fifth, but the former world No. 1 faded badly at Mission Hills Country Club, making two birdies and five bogeys in a round of 3-over 75 that left her at 5 under.

"I was lacking steadiness on my tee shot and I can't be satisfied with the way I played today," said Miyazato, who led after the first two rounds. "You can't win here unless you improve your score on the final day."

Ko, the youngest two-time major winner at 18 years and 11 months, captured her second straight major title, carding a 69 to finish at 12-under 276, one stroke ahead of England's Charley Hull (69) and South Korea's Chun In-gee (70).

Ko started the day one shot behind American leader Lexi Thompson, who was quickly overtaken by Ariya Jutanugarn of Thailand. Ariya jumped out to the lead with five birdies and one bogey in her first 10 holes.

But she stumbled coming in, making bogey at the 16th hole and opening the door for Ko who went on to seal victory on the final hole.

The world No. 1 opted to lay up to the par 5 18th then knocked her approach to a foot for birdie and the outright lead.

Ko, winner of last week's Kia Classic, made the traditional leap into Poppy's Pond adjacent to the 18th green after her victory.

"I'm proud I was able to make those clutch putts on the back nine," Ko said. "For these amazing things to be happening, it's incredible."