Novak Djokovic said Rafa Nadal had pushed him to the brink of exhaustion as his weary legs held him upright just long enough to see off the Spaniard in the longest Grand Slam final on record.

The Serb finally prevailed 5-7, 6-4, 6-2, 6-7, 7-5 in five hours and 53 minutes to win the Australian Open for the third time.

"I overcame everything, and that's the most important thing for me," Djokovic said when asked about his physical troubles that had hindered his quarter-final win over David Ferrer and semi-final defeat of Andy Murray.

"And to be able to mentally hang in there and physically, you know I mean, it was obvious on the court for everybody who has watched the match that both of us, physically, we took the last drop of energy that we had from our bodies.

"You know, I think it was just the matter of maybe luck in some moments and matter of wanting this more than maybe other player in the certain point.

Djokovic's crushing flat forehands did the trick for the world number one, allowing him to consistently drive Nadal deep behind the baseline and negate the Spaniard's stinging top-spin.

His inner strength also proved to be his trump card, something several observers felt he had been lacking in the past.

The Serb had retired in the 2006 French Open quarter-finals against Nadal when trailing by two sets and again a year later due to blisters in the Wimbledon semi-final against the same opponent.

He also failed to defend his Melbourne Park title in 2009 when he controversially pulled out of his quarter-final against Andy Roddick citing heat exhaustion on a sweltering day.

In the early hours of Monday, the steel that drove him to the world's top ranking and three Grand Slam titles in 2011 was evident again.

"I'm a professional tennis player. I'm sure any other colleague tennis player would say the same: we live for these matches," he added.

Djokovic seized the one opening Nadal gave him in the fifth set. Trailing 30-15 and 3-4 in the decider, and with the crowd firmly behind the Spaniard, he rallied when the world number two missed an easy backhand down the line with the court wide open.

Sensing the slightest hint of blood, Djokovic moved in for the kill.

He picked off Nadal's serve in the 11th game to give him a 6-5 lead and while he had to fight off a break point, he sealed his third successive Grand Slam title with a forehand winner.

"I had lots of chances to finish the match in the fourth, but he came up with some incredible serves and incredible points," Djokovoic said.

"So he deserved to prolong the match in the fifth set, and then really both of us could have won the match.

"And even when I was 4-2 down I still pushed myself up to the limit."