MELBOURNE (AFP) - Teenage world No.1 Lydia Ko added the Australian Open to her growing list of achievements with a two-stroke win at Royal Melbourne on Sunday.

The 17-year-old New Zealander became the youngest-ever world No.1 earlier this month and is now the youngest player to win the Australian Open crown.

It was her first tournament victory since moving to the top of the world rankings.

Despite the hot and steamy conditions, Ko finished at nine under 283 after a closing two-under 71 to claim the tournament from Australian-raised South Korean Amy Yang.

The pair dueled for the lead through the final round, with Yang carding a one-under 72 to finish at seven under 285.

Thailand's Ariya Jutanugarn was third at four under 288 after a final round 76.

Ko and Yang battled throughout the final round, with a 90-minute suspension of play for lightning helping Ko's cause.

While Ko had just dropped a shot on the eighth, Yang had birdied nine and was ready to putt for an eagle on 10 when the warning siren sounded.

Yang settled for a birdie after her ball circled the hole but failed to drop.

It gave her the lead but it did not last long with Ko adding two birdies on the back nine.

Yang also had two birdies, but bogeys on 15 and 17 snuffed out her challenge.

"I think that break was really good for me," Ko said.

"I had some lunch and got my stuff together there and I played much better after that."

Ko's record also includes being the youngest golfer to win a professional event, taking out the women's NSW Open when she was 14.

She said she loved playing in Australia and approached each tournament here with the mindset she could win.

"I've always played well in Australia, so it's always cool coming back here," she said.