The world No.3 - runner-up to Aryna Sabalenka at Melbourne Park last year - fended off eight match points against Russian Anna Blinkova but couldn't manage a ninth, falling 22-20 in the match tiebreaker on Thursday night.
The epic beat the previous record for the longest tiebreaker at a major of 20-18, set by Ukrainian Lesia Tsurenko and Hungarian Anna Bondar at Wimbledon last year.
Unseeded Russian Anna Blinkova overcome with emotion following her epic Australian Open win. (James Ross/AAP PHOTOS)
Blinkova had twice served for the match earlier in the third set but the 24-year-old Kazakh broke back each time.
Down 17-18 in the super tiebreaker, the 25-year-old Blinkova won an extraordinary 17-shot rally in which Rybakina had her running to all parts of the court.
In all, Blinkova saved six match points of her own as she went on to post the best win of her career.
"I just tried to stay focused on every point," said Blinkova after her 6-4 4-6 7-6 (22-20) triumph in front of a raucous Rod Laver Arena crowd.
"I had so many match points and I tried to be aggressive in these moments but my hands were shaking and my legs too.
"I tried to be calm ... and super happy to win in the end."
Elena Rybakina, last year's Open runner-up, saved eight match points before bowing out in 2024. (James Ross/AAP PHOTOS)
Blinkova had previously beaten a top-10 player twice - then-world No.8 Belinda Bencic in 2020 and  fifth-seeded Caroline Garcia at last year's French Open - but never one as highly-ranked as Rybakina.
The world No.57 has not progressed beyond the third round of a grand slam before but will get a fourth shot against Italian No.26 Jasmine Paolini, who beat German Tatjana Maria 6-2 6-3 earlier on Thursday.
10°C