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.
Gael Monfils said he was ready to "do some damage" after stunning Taylor Fritz on Saturday at the Australian Open in his first win over a top-five seed at a Grand Slam in almost 17 years.
A fired-up Novak Djokovic powered into the last 16 of the Australian Open on Friday in an ominous reminder of why he is a 10-time Melbourne champion, but he needed a medical break and used an inhaler.
Collins, 31, blew kisses to the fiercely partisan crowd, cupped her ear and even pointed to her backside after a stormy 7-6 (7/4), 4-6, 6-2 victory over Aiava, the last Australian woman in the draw.
The left-handed Californian Tien soaked up the applause at Margaret Court Arena after the biggest win of his young career following four hours and 48 minutes of seesawing action.
On-court coaching, previously banned and punishable by point deductions, disqualification or even suspension from tournaments is being positively encouraged at Melbourne Park with "coaching pods" at court level in the corners of the main stadiums.
Novak Djokovic made a slice of Grand Slam history on his way into the Australian Open third round on Wednesday but last year's women's finalist Zheng Qinwen was knocked out in the biggest shock so far.
The Spanish third seed showed no mercy to Japan's Yoshihito Nishioka, who was taught a 6-0, 6-1, 6-4 lesson on Margaret Court Arena in an 81-minute rout.
The normally ice cool "Queen Wen" got hot under the collar as she was sent packing 7-6 (7/3), 6-3 in the second round by world number 97 Laura Siegemund of Germany.
The feisty Russian, a three-time finalist in Melbourne, lost his cool in the third set before rallying to beat unheralded Thai Kasidit Samrej 6-2, 4-6, 3-6, 6-1, 6-2 on Rod Laver Arena.
The sixth seed from Kazakhstan demonstrated her pedigree as she manoeuvred the 16-year-old world junior number one from Australia to all parts of Margaret Court Arena.
