Yet to lose a set, the Belgian is in devastating form despite a foot injury which had threatened to sideline her and will play Russia's Anastasia Myskina for a place in the semis.
Self-confessed tennis bad girl, Myskina survived a red mist to beat ninth seed Chanda Rubin 6-7 6-2 6-2.
French schoolgirl Tatiana Golovin's amazing run at the first Grand Slam of the year came to an end, however. The 16-year-old was thrashed 6-2 6-0 by American doubles specialist Lisa Raymond, conqueror of Venus Williams in the previous round.
In the men's field, eighth seed David Nalbandian beat fellow Argentine Guillermo Canas 6-4 6-2 6-1 to reach the quarters here for the second year running.
The former Wimbledon finalist has not dropped a single set in his four matches so far and will play either Lleyton Hewitt or Roger Federer next.
Hewitt and Swiss second seed Federer meet in an eagerly-anticipated night match -- a repeat of their epic Davis Cup clash last year when the Australian came from two sets down to beat the Wimbledon champion in this stadium.
Clijsters had won all three of her matches against Farina Elia and never looked in any trouble against the Italian in their 73-minute encounter.
"I felt like this was good," she said. "I had to move well, move around a lot and I felt like I really enjoyed it as well."
Clijsters has conceded just 14 games in her four matches so far and remains well on track for her first major title after reaching the semi-finals in Melbourne the past two years.
She has lost in the final of three grand slams -- the 2001 French Open and the French and U.S. Opens last year.
Clijsters can expect to be tested a little
"She's obviously playing really well. I'll have to attack and make sure that I can get into an advantage situation a little bit from the start of rallies," Clijsters said.
Sixth seed Myskina battled past Rubin after a scratchy first set and is looking forward to the Clijsters showdown.
"If I play like I did in the second and third sets, it is going to be a good match," the Russian said.
"Against Kim, you just have to do your best. Not 100 percent, I have to give like 300 percent. It is really hard, though because she is the best one right now," Myskina said, before explaining why she had been so cross on court during her win over Rubin.
"He's kind of like a wall there...he has to show me something...show some emotions to me," grinned the Russian, referring to coach and former boyfriend Jens Gerlach.
"You know, yeah, I can get really angry sometimes...(but) he knows me, he knows that I don't really mean it...the whole thing that happens on the court.
"You know, I am the way I am. If nobody likes me the way I am, I'm sorry. But I think, you know, I'm really nice -- too nice," she laughed.
Raymond hardly raised a sweat as she ruined Golovin's run, racing past her inexperienced opponent in just 42 minutes.
Moscow-born Golovin, who celebrated her 16th birthday on Sunday, had beaten seeds Lina Krasnoroutskaya and Anna Smashnova-Pistolesi on her way to the fourth round but simply ran out of steam.
"I think I was getting a little tired," the French girl said. "It's my second week, I wasn't moving very well and I had to play my best tennis if I wanted to win. It didn't happen," added the wildcard entrant.
Raymond will play 22nd seed Patty Schnyder of Switzerland, who beat French 29th seed Nathalie Dechy 6-2 6-4.