Serena Williams staved off a spectacular fightback from world number one Simona Halep to win 6-1 4-6 6-4 and reach the quarter-finals of the Australian Open.
French Open champion Halep broke Williams' serve in the first game but that was the only one she managed for the rest of the opening set as the 23-time Grand Slam champion bulldozed her way through the set in 20 minutes, serving it out with an ace.
The victory was a major step towards the 37-year-old U.S. great equalling Australian Margaret Court's all-time record of 24 Grand Slam wins as she powered into the last eight.
It looked as if she would breeze through the match after the opening set mauling she had handed out but the world number one Halep had other plans as she fought back to level the contest at one set apiece 1-1 after breaking Williams a second time.
Following an attritional first few games, the seven-times Australian Open champion got the crucial break of serve in the seventh game of the decider and sealed the match in an hour and 47 minutes when Halep hit a forehand out.
"It was a really intense match and there were some incredible points but I love playing tennis... It's really cool to be back out and playing again on this court," Williams said in her courtside interview.
"I really needed to elevate my game, she's the number one player in the world and there's a reason why. In order for me to stay out there, I just had to play a little bit like I knew I could, and I did."
Elina Svitolina defeated Madison Keys in three sets to reach the quarter-finals for the second consecutive year.
The sixth-seeded Ukrainian battled for nearly three hours to see off Zhang Shuai in the previous round and showed impressive mental strength again in a 6-2 1-6 6-1 victory over American Keys.
A game lasting more than 10 minutes at 1-1 in the third was the key, with Svitolina, who won her biggest title at the WTA Finals last October, eventually holding serve and then racing to victory.
It is only the second time in the last six slam tournaments that Keys has not made at least the last eight.
Karolina Pliskova thrashed twice Grand Slam champion Garbine Muguruza 6-3 6-1 to reach the quarter-finals for the third time in succession.
The Czech seventh seed broke former Wimbledon champion Muguruza five times in the one-sided clash in the afternoon sunshine at Margaret Court Arena.
Needing only 24 minutes to win the second set, Pliskova earned two match points on Muguruza's serve and sealed the win when the out-of-sorts Spaniard smashed a backhand long.
Pliskova will meet the winner of top seed Simona Halep and Serena Williams for a place in the semi-finals as she continues her bid for a maiden Grand Slam.
US Open champion Naomi Osaka completed another comeback victory to overhaul 13th seed Anastasija Sevastova 4-6 6-3 6-4 and for her place in the quarter-finals.
The Japanese fourth seed, who had to fight back from a set down against Hsieh Su-Wei in her previous match, was far from her best as she struggled to hold serve and berated herself regularly during the sun-bathed clash at Rod Laver Arena.
She held firm when it counted, however, breaking Sevastova in the seventh game of the decider before sealing the match after one hour and 47 minutes with an imperious forehand down the line.
Osaka will play sixth seed Svitolina for a place in the semi-finals.
