Defending champion Novak Djokovic battled past Rafael Nadal in an epic, five-set Australian Open final that clocked in at 5 hours, 53 minutes - the longest title match in Grand Slam history - on Sunday.

Djokovic fought back from losing the first set to take a 2-1 lead, but he was taken to a gripping fifth set by a resurgent Nadal before winning 5-7, 6-4, 6-2, 6-7 (5/7), 7-5 for his third consecutive major title.

Djokovic, who picks up a check for $2.4 million, has beaten the Spaniard in three consecutive Grand Slam finals and seven consecutive title matches.

It was a match of wildly swinging fortunes that started before 8:00 pm in Melbourne on Sunday and did not wind up until 1:40 am on Monday.

The Serb cut a frustrated figure in the first set, slamming his racket to the ground when he was broken for the first time and falling one set behind.

A re-energized Djokovic found his rhythm in the second set, levelling the match on his fourth set point and, starting to dictate, ran away with the third set, overpowering Nadal and breaking him to love to win it 6-2.

The 25-year-old from Majorca, deposed from the top ranking by Djokovic after his defeat in last year's Wimbledon final, dug deep in the fourth set, getting back into the contest through sheer force of will.

The Spanish left-hander saved three break points in the eighth game, producing a fist-pumping celebration when he levelled at 4-4.

But then to add to the mounting tension, action was suspended while the roof was closed and the court dried due to rain.

When play restarted, the set went to a tie-break, with Nadal clinching the set at his first opportunity, as Djokovic went long and wide on the forehand.

In a dramatic fifth set Nadal secured a crucial break in the sixth game.

But with the Spaniard now suddenly looking the more likely winner, Djokovic battled back to break.

A stunning 31-shot rally at the start of the ninth game left Djokovic on his back, and Nadal then fought off a break point to hold.

But Djokovic broke in the 11th game when Nadal netted with a backhand, and he saved a break point before serving out for the championship.

The Serb ripped off his shirt in celebration and marched to his players' box flexing his muscles and then hugging his coach.

The match outstripped the 1988 US Open final between Mats Wilander and Ivan Lendl, which lasted 4:54, and also beat the Australian Open record of 5:14 set by Nadal and Fernando Verdasco.