Madison Keys fought back from a set down on Thursday to shock Iga Swiatek in a nail-biter and set up an Australian Open final against two-time defending champion Aryna Sabalenka.

The 19th seed battled 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 swept aside Paula Badosa in straight sets.

Five-time Grand Slam champion Swiatek had not dropped her serve since the first round but was broken eight times by Keys, who saved a match point on her way to edging a titanic battle. It will be the American's first final in Melbourne, and only her second in Slams, and she broke down in tears after finally getting over the line in 2hr 35min.

It was the first time an Australian Open semi-final had been decided by a third-set 10-point tiebreak.

"That match was just such a high level and she played so well," Keys, 29, said.

"I felt like I was just fighting to stay in it and then obviously really kind of ran with the second and then the third was just a battle.

"To be able to be standing here and be in the finals is absolutely amazing and I'm so excited that I get to be here on Saturday."

Keys confessed she couldn't recall much detail about the final set where she saved a match point.

"In the third set, it was just so up and down. I feel like I blacked out at some point," Keys smiled.

"Just to be able to stay in it and just keep fighting and then a 10-point tiebreaker for a dramatic finish."

Earlier, Sabalenka put her close friendship with Badosa aside to stay on track for a 26-year first.

The Belarusian world number one romped home 6-4, 6-2 on Rod Laver Arena against 11th seed Badosa.

Keys predicted a slug-fest between two of the hardest ball-strikers in the women's game in Saturday's showpiece. "Definitely some big hitting. I think that is going to happen," Keys said.

"Not a lot of long points but she is obviously going for her third Aussie Open and I'm excited to get to play here." Sabalenka is closing on a third consecutive Melbourne crown -- something that hasn't happened this century.

The last person to achieve the feat was Martina Hingis in 1999 and only four other women have completed the three-peat -- Margaret Court, Evonne Goolagong, Steffi Graf and Monica Seles.

Court was in the stadium watching.

"Honestly, I don't know. I'm so proud of myself. I'm proud of my team that we're able to put ourselves in such a situation," Sabalenka said of being on the cusp of a third Melbourne Park title.

"It's a privilege. If I'm able to put my name into history, it will mean a lot. It will mean the world to me."

Sabalenka last year described Badosa as her "best friend" and "soulmate" and said she was "super happy" that they got to play each other on such a big stage.

"I hope she's still my friend. I'm sure she'll hate me for the next hour, day or two, but I'm okay with that, I can handle that," she added.

Despite losing, Badosa's run to the last four capped a remarkable comeback for the Spaniard after a brutal back injury in 2023 had her considering quitting tennis.

Instead, her Melbourne exploits will return her to the top 10 for the first time since October 2022. Keys will also return to the top 10.