Top-seeded SimonaHalep served for the match four times before prevailing 4-6, 6-4, 15-13 over American Lauren Davis in a marathon third round match at Rod Laver Arena.
The two broke a record, playing the most games of any women's match in Australian Open history.
Halep said she was "almost dead" after the match that went three hours and 45 minutes. Halep ended up running over four kilometers throughout the match.
Halep saved three match points in the 22nd game of the third set at 0-40 and Davis saved five break points in the 23rd game. The final set took 2 hour, 22 minutes and Halep won on her first match point when Davis hit a forehand wide along the sideline.
Davis twice had medical timeouts in the final set to have blisters on both feet treated.
Halep will play the winner of Saturday's later match between local hope Ashleigh Barty and Naomi Osaka.
In other women's third-round matches, sixth-seeded Karolina Pliskova beat Lucie Safarova 7-6 (6), 7-5 and No. 8 Caroline Garcia beat Lucie Safarova 6-3, 5-7, 6-2. Garcia will play Madison Keys in the fourth round.