The Polish superstar had not dropped a set in her previous five matches this campaign and was on track early to advance in pursuit of a sixth grand slam title.
But a determined and gritty Keys fought back from a set down and a match point down to win 5-7 6-1 7-6 (10-8) at Rod Laver Arena on Thursday night to set up a title decider against two-time defending champion and world No.1 Aryna Sabalenka.
Iga Swiatek was so close to reaching her first final in Melbourne. (Joel Carrett/AAP PHOTOS)
The 19th seed Keys finished the match in tears after holding her nerve during a see-sawing match tiebreak to reach her second career grand slam final - and first in more than seven years.
"I'm still trying to catch up to everything that's happening. I'm in the finals," an emotional Keys said on-court.
"That match was just such a high level and she played so well.
"I feel like I was just fighting to stay in it and really ran with it in 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."
A raft of unforced errors hurt Keys in the opening set, but the 29-year-old found her groove in the second.
The 25-minute demolition job was the first set world No.2 Swiatek had dropped all tournament.
Keys lost her serve at five-all in the third set and faced match point at 40-30 on Swiatek's delivery, only to pull out a fine service return to save the day before going on to send the match to a tiebreak.
🔓 She's done it! — #AusOpen (@AustralianOpen) @Madison_Keys wins four of the final five points of the super tiebreak to book her place in Saturday's final!@wwos • @espn • @eurosport • @wowowtennis • #AusOpen • #AO2025 pic.twitter.com/k7gVLVtibZJanuary 23, 2025
"Even though I lost the first set, I felt like I was playing some better tennis at the end of it and I actually had a little bit of momentum going into the second set," Keys said.
"To be able to run with that second set and really just settle was really nice.
"The third set was so up and down, and there were so many big points.
"I feel like I blacked out at some point and I was just out there running around.
"To be able to stay in and keep fighting and then a 10-point tiebreaker for an extra dramatic finish.
"At the end I felt like we were both battling some nerves and really just pushing each other.
"It just became (about) who can get that final point and who can be a little bit better than the other one. I'm happy it was me."
In reaching the final, Keys has matched her best result at a grand slam.
Down match point? No worries 👌— #AusOpen (@AustralianOpen) @bondisands • #BondiSands • #StayCool • #AusOpen • #AO2025 • @wwos • @espn • @eurosport • @wowowtennis pic.twitter.com/2TYZ04NnvZJanuary 23, 2025
The former world No.7, who also made the last four at Melbourne Park in 2015 and 2022, was beaten by Sloane Stephens in the 2017 US Open final.
Now she's out to go one better, but faces a huge hurdle in the powerful Belarusian Sabalenka, who is aiming to become the first woman since Martina Hingis (1997-1999) to claim three straight titles at Melbourne Park.
"Definitely some big hitting is going to happen - not a lot of long points," Keys said.
"She's going for her third Aussie Open and I'm excited to get to play her.
"I'm really excited for the challenge but Saturday is very far away in my brain right now."
