Serena Williams won her sixth Australian Open and 19th career Grand Slam with a hard-fought win over bitter rival Maria Sharapova on Saturday, consolidating her place among the game's legends.

The 6-3, 7-6 (7/5) triumph means the American world number one overtakes 18-time major champions Martina Navratilova and Chris Evert to go clear second on the all-time Open-era Grand Slam winners' list, three behind Steffi Graf.

Australia's Margaret Court, who played many of her match before the Open-era, has 24 titles. Evert, commentating on ESPN, backed Williams to eventually overtake Graf's mark "if she stays healthy, if he stays motivated".

"Standing here with 19 championships is something I never thought would happen, I went on the courts with just a ball and a racquet and hope and that's all I had," said Williams, at 33 the oldest women to win the Melbourne title.

The first Australian final in a decade to feature the tournament's top two seeds was a one-sided affair in the opening set, although Sharapova rallied to make a contest of it in the second, saving two championship points before falling to a third.

The win extends Williams' decade-long run over the Russian to 16 matches, with the second seed hailing her rival's "incredible achievement".