The victory also thrust him alongside Andre Agassi, Roger Federer and Novak Djokovic as the only men to successfully defend their Melbourne Park titles this century.

But it proved more misery for Germany's Zverev, who remains one of the world's best players never to taste Grand Slam glory, falling short once again in his third big final.

Ice-cool Sinner proved to be a tower of mental strength in Australia, with his defence coming against the backdrop of an ongoing doping case after he twice tested positive for traces of the steroid clostebol last year.

Hanging over his head has been a World Anti-Doping Agency appeal against his exoneration, with the global body seeking a long ban.

A hearing is scheduled at the Court of Arbitration for Sport (CAS) for April.

But he cast all the worries aside to notch a 19th career title and extend his incredible win streak to 21 matches.

Last year, Sinner needed five sets to tame Daniil Medvedev and win his first Grand Slam, but it never looked like going the distance this time.

He opened with a statement ace and won his first two service games to love, with Zverev struggling to get himself into the contest.

The German fought back to save two break points and hold for 2-2, serving his way out of trouble.

He began to find his radar, taking four points off the next Sinner serve in a game that went to deuce twice as the rallies built.

Racing clear

But the dam finally burst in the eighth game.

Zverev saved three break points but had no answer to a fourth when he was beaten by a blazing passing shot to slump 5-3 behind.

Sinner took the set in 46 minutes and kept the pressure on in the second as cracks began to appear in his opponent's game.

The Italian has a phenomenal ability to turn recovery shots into momentum-changing ones and he raced 15-40 clear on the Zverev serve at 1-1.

Once more, the second seed dug deep to cling on.

From then on they couldn't be separated and it went to a tiebreak where Sinner got a lucky net cord that dribbled over to break for 5-4 and he streaked to a two-set lead.

Sinner has won all four tiebreaks he's played in Melbourne and 16 from his last 18.