The 23-year-old came through a tense battle between the world's top two players 6-3, 7-6 (7/4), 6-3 on Rod Laver Arena, raising his arms in the air and looking to the sky in celebration.
The victory earned the Italian world number one his third Grand Slam crown.
The former world number one responded on Saturday, posting a photo of an MRI taken of his left hamstring on the social media platform X with the caption: "Thought I'd leave this here for all the sports injury 'experts' out there."
It is Keys's first major title, having reached a second Grand Slam final eight years after her first in New York. She lost on that occasion to Sloane Stephens
Sinner's coach Darren Cahill said it was no surprise for him to see his young charge back in the final, but they were wary of the threat posed by Zverev's overarching desire to finally win a Slam.
The American battled injury and self-doubts last year and curtailed her season early, in October, to get married.
Swiatek said she made far too many mistakes against Keys on Rod Laver Arena and hoped to draw lessons from it.
The 19th seed powered through a thrilling semi-final on a final-set tiebreak against the world number two 5-7, 6-1, 7-6 (10/8) after Sabalenka had earlier swept aside Paula Badosa in straight sets.
The Italian top seed faces Ben Shelton on Friday, just two matches away from a first successful Grand Slam title defence after winning his maiden major crown in Melbourne last year.
Nick Kyrgios struggled to deal with the furore over his shock second round meltdown at the Australian Open but said the return to a team environment with Davis Cup had helped him through it.
Roger Federer dropped hints that his great career may be drawing to a close after his age-defying win over his Grand Slam nemesis Rafael Nadal at the Australian Open.
Rafa Nadal's hopes of a 15th grand slam title were crushed by an inspired Roger Federer in the Australian Open final but the rejuvenated Spaniard is already rubbing his hands together at the prospect of a "special" season on clay
Roger Federer wins a thrilling, five-set Australian Open final against his great rival Rafael Nadal to clinch a record-extending 18th Grand Slam.
American Abigail Spears and Colombian partner Juan Sebastian Cabal swept to a first Grand Slam mixed doubles title Sunday with a straight-sets victory at the Australian Open.
Serena Williams clinched a record 23rd grand slam title at the Australian Open on Saturday but spent most of the immediate aftermath talking about her older sister Venus.
Second seeds Bethanie Mattek-Sands and Lucie Safarova took out the Australian Open women's doubles title on Friday to be crowned Grand Slam champions for a fourth time.
Serena Williams ended the fairytale run of Mirjana Lucic-Baroni at the Australian Open on Thursday with a crushing 6-2 6-1 win that set up a final against her sister Venus.
Venus Williams drew on the experience of 73 grand slam campaigns to come from a set down for a 6-7(3) 6-2 6-3 victory over fellow American Coco Vandeweghe on Thursday to set up a possible Australian Open final against her sister Serena.
Rafael Nadal claimed a dominant straight-sets win over world number three Milos Raonic to advance to the semifinals at the Australian Open on Wednesday.
