Kiwi teen Lydia Ko smashes Tiger Woods' record by nearly four years to become the youngest golf world No 1.

Lydia Ko might be the new world No 1 golfer, but she was "miffed" she didn't win the LPGA Tour's season-opening event.

Ko's coach David Leadbetter told Stuff.co.nz her pupil would rather have won the Coates Golf Championship in Florida than taken the No 1 spot, but she did appreciate the fact she was the youngest to ever hold the mantle was special.

"I'm not sure the No 1 thing has really sunken in yet," Leadbetter said.

Getty Images WORLD NO 1: Kiwi golfer Lydia Ko has become golf's youngest ever world No 1, at age 17.

"She's very happy, there's no denying it, but she's a little miffed at herself for not winning the tournament."

Ko finished in a three-way tie for second at the US$1.5 million (NZ$2.07m) event. She fired a final round one-under 71 to finish the 72-hole tournament at 15-under par, one back from Korean winner Na Yeon Choi.

Ko led by four at one stage, but Choi pegged her back before a double bogey six on the par-four 17th by Ko, gave Choi a one-shot advantage which she held down the final hole.

Leadbetter said even he didn't expect Ko to be No 1 so soon.

"I was surprised with how consistent she was last year. We obviously all knew she was a very talented golfer, but have a look at how well she went and how many times she put herself in contention.

"To be honest, I was surprised at that and surprised she's got to No 1 so soon, but she deserves it. She's played consistently good golf and nothing bothers her."

It was one bad hole which cost Ko, a double bogey at the par four 17th.

"I thought she played beautifully yesterday [Ko shot a seven-under 65] and today was unfortunately not so good. She just had a couple of loose shots and, unfortunately for her, they came at the wrong time.

"But what an achievement, to be the youngest ever. It's an amazing feat and one New Zealand should be really, really proud of."

She takes the record from American golf superstar Tiger Woods, who first became men's golf world No 1 aged 21 years, 167 days. Ko was today 17 years 283 days old.

Jiyai Shin was the previous youngest women's No 1 at 22 years and five days.

It didn't all go Ko's way today despite the 17-year-old New Zealander opening up a four-shot buffer early in the final round courtesy of birdies on the opening two holes.

Ko sunk two 20-foot putts on one and two, the second of which was a big left to right breaker that just caught the outside of the hole and dropped.

She birdied the fifth, from off the green, and bogeyed the eighth to turn at two-under.

But Choi kept coming at Ko and birdies at 12 and 14 gave the Korean a one shot buffer.

READ MORE: Recap - look back at Stuff.co.nz's shot-by-shot commentary

Choi got to five under for her round and had a one shot lead over Ko as they stood on the tee for the 118m par-three 15th.

When Choi hit her tee shot to within four feet of the pin and Ko pulled hers 70-feet to the left, Choi looked certain to extend her advantage.

But Ko sunk her monster putt. It was a tough one which broke then gained speed as it got closer to the hole, but Ko knew it was going in and celebrated by punching her arm into the air just before it dropped.

The pressure got to Choi who not only missed her slippery four-foot birdie putt, but also the straight forward three-foot return for par.

From one behind and in trouble, Ko had a one-shot lead.

Both players parred the 16th, but it all changed on the par-four 17th.

Ko found the fairway bunker off the tee then went further right with a poor shot which forced her to chip back to the middle.

Her fourth - from 60m - went short and rolled off the green. Her chip was far from her best, but she then sunk a handy 15-foot putt for double bogey.

Choi parred it to head to the 18th with a one shot buffer.

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