Golfing wunderkind Lydia Ko fought off a final round challenge from American Amelia Lewis and Australia’s Stacey Keating to take out the New Zealand Women’s Open at Clearwater near Christchurch on Sunday.

The top-ranked amateur became the first New Zealander to win the title when she sunk a five foot putt at the 18th to secure a one-stroke victory over Lewis, with Keating a further stroke back in third.

The 15-year-old was the joint-overnight leader but showed nerves of steel to battle back after first Keating, who shot seven-under for the day, and later Lewis caught and then overtook her during the final round.

But the nerves wore down after the final hole, when Ko was surprisingly ambushed after the winning putt by some unexpected tears.

“I have no idea why I cried here – I guess it meant more,” she said afterwards.

“It’s our national open so to win meant a lot. I’m not a person that shows expression of feelings that much, but I guess the tears showed it.”

Ko carded a final round 68 to go with her earlier 70 and 68, finishing 10-under par over the 54-hole tournament.

Lewis had earlier matched Ko stroke for stroke but faltered at the 18th, three-putting to bogey the par four hole.

That left the way open for Ko, and although she found the rough from the tee, she recovered well to hit the green with her approach shot and two-putt for par.

Ko had missed a number of chances throughout the day but hung in one shot behind the American who had managed six birdies, an eagle and one bogey in an explosive first 13 holes.

Ko said her consistency, and some solid putting, proved key to the win.

“It’s never easy to play good every single day – I played pretty well the last three days, but I guess it depended on the putts.

“I think I putted better today than the first day, there weren’t any huge mistakes.”

Ko became the youngest player to win a professional event when she took out the NSW Open as a 14-year-old last January, following that up with a victory at the Canadian Open in August.

It’s the fourth time the Korea-born New Zealander has contested the New Zealand Open. She tied for seventh on her debut in 2010 as a 12-year-old, finished fourth the following year, then faded to take 17th last year after leading going into the final round.

Australian pair Nikki Campbell and Sarah Jane Smith finished with share of fifth spot at six-under.