Unseeded Russian Anna Blinkova said it was the best day of her life after beating last year's Australian Open runner-up Elena Rybakina Thursday following the longest tie-break in a singles match in Grand Slam history.
The world number 57 Blinkova outlasted the third seed 6-4, 4-6, 7-6 (22/20) in a gripping encounter on Rod Laver Court that lasted two hours and 46 minutes.
But the first two sets were completely forgotten in an astonishing 42-point tie-break that lasted more than half an hour.
Blinkova saved six match points before converting on her 10th match point to advance to the third round in Melbourne for the first time.
The previous tie-break record at a Grand Slam was 38 points, which happened on two occasions - at the 2007 Australian Open and at last year's Wimbledon.
"I don't know what to say, it was super tough," said a disbelieving Blinkova. "I just tried to stay focused on every point.
"I had so many match points and I tried to be aggressive in these moments, but my hands were shaking, my legs too. I tried to be calm as far as I could and I am super happy to win.
"I was telling myself 'go for it'. I was also telling myself 'just stay solid, stay solid, solid, solid, and just putting the ball in the court, into the court, in the court', and finally it worked out.
"This day, I will remember for the rest of my life, especially on this court with this crowd. I will never forget it. It is the best day of my life so far."
Former Wimbledon champion Rybakina came into the tournament on a high after winning the Brisbane International and was considered one of the favourites in Melbourne.
The Kazakh world number three, 24, was unable to muster a single break point in the opening set as Blinkova took charge.
Rybakina fell behind early in the second set but broke back immediately and repeated the feat in the 10th game to level the match.
There were six breaks of serve in a chaotic final set, with 25-year-old Blinkova unable to convert two match points in the 12th game.
After a see-saw tie-break, Blinkova made her move by winning a tricky 12-point rally that ended with a deep overhead winner.
She converted her final match point after Rybakina missed a backhand.
Blinkova will face 26th-seeded Italian Jasmine Paolini in the third round.