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.
Ever since bursting on the scene as a 17-year-old in 2019, the Italian has been touted as one of tennis' future greats.
Jannik Sinner stormed back from two sets down to beat Daniil Medvedev in a gruelling five-set Australian Open final on Sunday and win his first Grand Slam.
Since Stan Wawrinka won his only title in Melbourne in 2014, Novak Djokovic has picked up six trophies, Roger Federer has won two and Rafael Nadal has won one.
The Belarusian world number two has yet to drop a set in Melbourne this year
Former US Open champion Medvedev will hope to get third time lucky when he meets Italian youngster Jannik Sinner on Sunday
The Italian ended the Serb's record 33-match winning run at Melbourne Park.
Formidable world number two Aryna Sabalenka blasted past Coco Gauff into the Australian Open final on Thursday to keep her title defence on track.
Third seed Daniil Medvedev was forced to dig deep into his reserves to outlast Hubert Hurkacz 7-6(4), 2-6, 6-3, 5-7, 6-4 in the tightest of quarterfinals on Wednesday and reach the last four of the Australian Open for third time.
Novak Djokovic said he felt "trapped" in the heat during his battling quarter-final win against Taylor Fritz on Tuesday, which left him on track for a record-breaking 25th Grand Slam title.
"Happy, really proud of the fight I showed today," said Gauff, who had never progressed beyond the fourth round at Melbourne Park in four previous attempts.
