Gauff outclassed Swiatek 6-4 6-2 to record a fourth straight win over the world No.2 and force a mixed doubles decider in a dramatic semi-final at Ken Rosewall Arena on Saturday night.
But brought back to play alongside Christian Harrison, Gauff was powerless to stop the inspirational Polish pair of Katarzyna Kawa and Jan Zielinski from reprising the brilliance which had also sent Australia spinning out of the $17 million mixed team showpiece in the quarters.
Holding firm in two tiebreaks, the Polish pair, who'd beaten Storm Hunter and John Patrick-Smith in the previous night's decider, this time prevailed 7-6 (7-5) 7-6 (7-3) after midnight to reach a third-straight final, up against Stan Wawrinka-inspired Switzerland, on Sunday night.
Swiatek's breakthough Wimbledon triumph last July completed the third leg of a rare career slam for the 24-year-old, who needs a Melbourne Park major to complete the set.
But Gauff's latest victory over the six-times grand slam champ must have cast doubts into the former world No.1's mind.
Poland had taken the early lead in the second semi-final when Hubert Hurkacz rebounded brilliantly from a sapping three-set loss on Friday night to local hero Alex de Minaur to edge out Tayor Fritz 7-6 (7-2) 7-6 (7-1) in a big-serving shootout.
"Hats off to Hubert who's coming back after seven months away to play incredible tennis and inspiring all of us to play like we did today," said the delighted Zielinski. "He's just been an inspiration to all of us."
Before the re-run of last year's final between the US and Poland, invincible tennis super mum Belinda Bencic and retiring ironman Wawrinka had earlier on Saturday led the Swiss into a maiden final with heroic displays in Sydney's searing heat.
Just as in Switzerland's three previous ties, Bencic and Wawrinka were the heart and soul of the epic 2-1 victory over Belgium.
After surviving a third-set tiebreaker to defeat Elise Mertens 6-3 4-6 7-6 (7-0) in the opening singles match, Bencic teamed with Jakub Paul to win their third decisive mixed doubles match of the tournament in a rollercoaster encounter stretching almost eight hours.
Unbeaten in four singles and four mixed matches this week, Bencic - the Tokyo Olympic gold medallist and former world No.4 - and Paul won 6-3 0-6 [10-5] after regrouping from a second-set collapse when they won just 12 points.
The mixed victory was necessary after Zizou Bergs continued his impressive campaign with a 6-3 6-7 (4-7) 6-3 triumph over Wawrinka to level the tie as the temperature exceeded 40 degrees during Sydney's summer heat wave.
Despite Wawrinka's defeat, Bencic and Paul credited the 40-year-old triple grand slam winner as the inspiration behind their unlikely march to the final.
The former Australian, French and US Open champion needed endless ice packs and towels to stay on court but pushed Bergs for two-and-a-half hours before succumbing.
"He's just doing an amazing job to give us the energy," Paul said.
"A great job from Stan to keep Zizou as long as possible on the court.
"So we try to give him back as much as possible. He's just a role model for him to play three hours and then be here (supporting courtside) for the first point of the doubles.
"And it's just great to play with Belinda. Just hats off to her to play almost three hours and then come out again for the doubles.
"That's amazing."
