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.
Novak Djokovic has won the Australian Open a record nine times but a 10th title in Melbourne this month will be the most satisfying of all after his humiliating ban a year ago.
Players at this month's Australian Open will not be required to take COVID-19 tests and could play even if they had the virus, tournament director Craig Tiley said on Monday.
Aryna Sabalenka fired an Australian Open warning shot Sunday by winning her first title since 2021 at the Adelaide International, beating rising Czech teenager Linda Noskova 6-3, 7-6 (7/4).
Two-time Australian Open champion Naomi Osaka became the latest star to pull out of the opening Grand Slam of the year Sunday, leaving the tournament deprived of some of the biggest names in the game.
Unheralded Czech teenager Linda Noskova stunned world number two Ons Jabeur Saturday to make her first-ever final at the Adelaide International, dealing the Tunisian a demoralising blow ahead of the Australian Open.
World number five Aryna Sabalenka surged into the final of the Adelaide International Saturday, crushing Romanian veteran Irina-Camelia Begu for the loss of just five games.
US Open champion Carlos Alcaraz said on Friday he will miss the Australian Open, the first Grand Slam of the season, after injuring his right leg in training.
Former world number one Daniil Medvedev set up an Adelaide International semi-final against either Novak Djokovic or Denis Shapovalov Friday with a command performance in the countdown to the opening Grand Slam of the year.
Former world number one Daniil Medvedev locked in an all-Russian Adelaide International quarter-final with Karen Khachanov Wednesday, while Aryna Sabalenka stormed back to book her place in the last eight.
Novak Djokovic swept to victory in his first singles match on Australian soil since being deported a year ago, crushing Constant Lestienne at the Adelaide International on Tuesday to kick-start his bid for another Grand Slam title.
