Serena Williams won her 19th Grand Slam title, continued her unbeaten run in six Australian Open finals and extended her decade-long domination of Maria Sharapova with a commanding 6-3, 7-6 (5) win on Saturday night.

Williams, coughing frequently and still affected by a recent cold, controlled the first set around a rain delay in the sixth game, when the match was stopped for 13 minutes for the roof to be closed.

Top-ranked Williams returned from the break and fired an ace to start a run of six straight points. She was broken while serving for the set but broke Sharapova for a third time to clinch it.

She is now second only to Steffi Graf (22) on the list of major winners in the Open era.

The 33-year-old Williams, the oldest winner of the Australian women's title in the Open era, won the first six points of the second set and seemed on course for another lopsided victory before Sharapova hit back in a gripping second set.

Sharapova saved a match point in the 10th game, bravely hitting a forehand winner down the line — applauded by Williams — and twice held serve to stay in the match.

She forced a tiebreaker and then took the first point off Williams when she leaped into a service return down the line.

But Williams rallied again and relied on her serve to keep the points short. She fired 15 of her 18 aces in the second set, including one on her third match point to seal the match.

Williams has now won 16 in a row and is 17-2 in career matches against five-time major winner Sharapova, who hasn't won a head-to-head meeting since 2004.

Williams' six Australian titles — in 2003, '05, '07, '09 '10 and'15 — have included two victories in finals against Sharapova, who won at Melbourne Park in 2008.