Novak Djokovic held off Dominic Thiem to beat the Austrian 6-4 4-6 2-6 6-3 6-4 and seal an eighth Australian Open title.
The pre-tournament favourite, Djokovic had surprised no-one with his business-like march through the draw, dropping just one set on his way to an eighth final.
And it looked like it would be a procession to a 17th Grand Slam title as he cruised to the first set.
However, Thiem fought back, sealing sets two and three to put himself within touching distance of a stunning upset and a first Grand Slam.
An agitated Djokovic took aim at umpire Damien Dumusois at the changeover at the end of the second set, and then went on to lose the third set, but regrouped to regain his composure and send the final to a deciding fifth set.
And the 32-year-old secured the decisive break in the third game of the set before holding off a spirited Thiem to win his eighth title at Melbourne Park.
Djokovic, Rafael Nadal and Roger Federer have now won 13 Grand Slam titles in succession, dating back to Federer's 2017 title in Melbourne.
Thiem, seen as one of the greatest hopes to end the Big Three domination, was consigned to his third defeat in a major final following losses in the last two French Open deciders to Nadal.
"Unreal what you are doing through all these years. You and two other guys have brought men's tennis to a completely new level," the 26-year-old told Djokovic at the trophy ceremony.
While Thiem started heavy-legged after spending a total of eight hours beating Alexander Zverev and Nadal in his previous two matches, Djokovic charged out of the blocks to take the first set.
But the match turned on its head at 4-4 in the second when Djokovic became flustered after being called twice for breaching the service clock.
He returned to his chair fuming and paused to sarcastically pat chair umpire Damien Dumusois's shoe, telling the Frenchman: "Great job, man, you made yourself famous in this match, especially for the second one. Well done."
Conceding the set with a terrible backhand, a shellshocked Djokovic lost six games in a row as Thiem, blasting winners virtually at will, roared to a 4-0 lead in the third.
Something was amiss with the Serb and he called for the trainer after holding serve. But he underwent no treatment and resumed after an exchange of words.
He made a fist of digging in, saving three set points but a wayward forehand on the fourth gave Thiem the lead.
It looked gloomy for Djokovic, who had destroyed Nadal in three sets in the 2019 final.
But the match turned again when Thiem gave up a double-fault to concede two break points, then blasted a forehand long to fall 5-3 behind in the fourth set.
In a flash, Djokovic had served out the set to love, sealing it with an ace.
Having spent about six hours more time on court than Djokovic through the tournament, the strain of a long campaign began to tell on Thiem but he refused to crumble in the fifth.
He had two chances to break back in the fourth game but Djokovic nervelessly cancelled the threat before holding firm in the nerve-jangling finish.