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.
"I did everything almost perfectly. In our Miami 2022 match it was closer. It was a good match today as well. I pushed him to the limit in every point," said Alcaraz, who set up a clash with sixth seed Alexander Zverev.
The key difference was the unforced error count, with Borges making 66 to Medvedev's 34
"I need to take a little bit of time to breathe because my heart I feel is going to jump out of my body," Yastremska said.
Novak Djokovic marked a rare daytime appearance at the Australian Open with a dominant victory over Adrian Mannarino on Sunday as the 10-times champion flirted with a 'triple bagel' before sealing a 6-0, 6-0, 6-3 win to reach the quarter-finals.
Top seed Iga Swiatek crashed out of the Australian Open on Saturday, losing 3-6, 6-3, 6-4 to Czech teenager Linda Noskova in the third round as her bid for a maiden Melbourne Park title and fifth Grand Slam trophy fell apart.
Tennis great Rod Laver suggested Saturday that engravers could start putting Novak Djokovic's initials on the Australian Open trophy, with something "miraculous" needed to prevent him winning an 11th title.
Novak Djokovic has opened up on how he riled Roger Federer when he broke onto the scene as a cocky upstart but said it only fired up his quest to become the best player in the world.
World number two Carlos Alcaraz dropped a set Thursday before rediscovering his mojo to battle into the Australian Open third round, coming good when it mattered.
Iga Swiatek came back from the brink to beat unseeded American Danielle Collins in the second round of the Australian Open on Thursday, extending her winning run to 18 matches.
Russian 16-year-old Mirra Andreeva put her school work to one side Wednesday and instead underlined her huge potential by crushing sixth seed Ons Jabeur in under an hour at the Australian Open.
