Japan's Naomi Osaka has become the new women's world number one after winning the Australian Open final against Petra Kvitova in three gripping sets at Melbourne Park.

Osaka backed up her victory in last year's controversial US Open final against Serena Williams to claim her second major title, beating Kvitova 7-6 (7-2), 5-7, 6-4 in two hours and 27 minutes at Rod Laver Arena.

She becomes the first Japanese player to hold the number one ranking, moving up to the top spot from number four.

It had appeared Osaka was headed for a straight-sets win when she held three championship points at 5-3 in the second on the Kvitova serve.

But the Czech eighth seed showed nerves of steel to save all three and hold serve, much to the frustration of her 21-year-old opponent.

Even at that point, given the strength of the Osaka serve, it seemed the fourth seed would be able to safely serve out the set.

Kvitova, however, broke Osaka and secured a second break in a four-game winning streak to clinch the set and force a third and deciding set.