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.
World number one Iga Swiatek was knocked out of the Australian Open Sunday as Wimbledon champion Elena Rybakina blew the women's draw wide open by beating the red-hot favourite in straight sets.
Sebastian Korda says he's "the worst athlete" in his high-achieving sporting family, but with a little help from tennis legend Andre Agassi the rising American is working hard to change the dynamic.
Andy Murray and Novak Djokovic will have to rev their bodies into action when both attempt to reach the fourth round of the Australian Open on Saturday.
Defending champion Rafael Nadal crashed out of the Australian Open in round two to 65th-ranked American Mackenzie McDonald in a major upset Wednesday, his worst Grand Slam result in seven years.
Andy Murray stunned Italian 13th seed Matteo Berrettini on Tuesday, saving a match point to prevail over five gruelling sets and book a spot in the Australian Open second round.
Tennis Australia on Tuesday banned Russian and Belarusian flags at the Australian Open after Ukraine's ambassador demanded action when they were seen among the crowd.
Novak Djokovic makes his eagerly anticipated return to the Australian Open on Tuesday and women's world number two Ons Jabeur will also launch her title bid.
Teenager Shang Juncheng created a slice of history Monday by becoming the first male Chinese player to win an Australian Open main draw singles match.
Sam Stosur will bid a bittersweet farewell to home fans at the Australian Open but will not be straying far from the game, the 38-year-old major winner said on Sunday.
Defending champion Rafael Nadal admitted Saturday he felt vulnerable heading into the Australian Open after two straight defeats in the build-up and said that Novak Djokovic was clear favourite.
