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.
Wozniacki, 32, bowed out in 2020 after winning 30 WTA titles including her sole Grand Slam triumph at the Australian Open in 2018
World number one Iga Swiatek defeated Australian Open champion Aryna Sabalenka in straight sets to win her second consecutive Stuttgart title on Sunday.
The Australian Open set a Grand Slam attendance record with more than 900,000 spectators visiting over three weeks, organisers said on Tuesday, despite the absence of some big-name players and schedule disruptions due to rain.
New Australian Open champion Novak Djokovic said on Monday he hopes to return to action in a month's time but is "not sure" how quickly his injured hamstring will heal.
Novak Djokovic, who won a record-equalling 22nd Grand Slam title on Sunday, is driven on through controversy by his determination to be the greatest ever.
Novak Djokovic's father was absent from his son's player's box for the Australian Open final Sunday following a controversy over images of him posing with a Russian flag featuring Vladimir Putin.
Facts and figures ahead of Sunday's Australian Open men's final (x denotes seeding):
Novak Djokovic has won all nine of his previous Australian Open finals so confidence is sky-high as he bids to equal Rafael Nadal's Grand Slam record and return to world number one.
An emotional Aryna Sabalenka battled back from a set down to beat Elena Rybakina and win the Australian Open on Saturday for her first Grand Slam title.
Australian Open chief Craig Tiley on Saturday advised Novak Djokovic's family to be "really careful" of people using the tournament's global exposure as a platform for "disruptive" purposes.
