The former world No.1s - both Australian Open champions and Fed Cup teammates against Australia on the same Brisbane court five years ago - won quarter-finals on Friday in contrasting fashion.
World No.2 Sabalenka, the defending champion at Melbourne Park, crushed fifth seed and world No.18 Daria Kasatkina 6-1 6-4.
Azarenka, 34, had earlier survived Jelena Ostapenko's spicy best 6-3 3-6 7-5 over two and a half hours.
Wimbledon champion and Australian Open runner-up Elena Rybakina will play 19-year-old Czech Linda Noskova in the other semi-final on Saturday.
Azarenka is eyeing a third Brisbane title but first since the birth of her son in 2016, the two-time Open champion crushing 16 aces to defy Ostapenko.
Top seed Aryna Sabalenka has been untroubled on her way to the Brisbane International semi-finals. (Zain Mohammed/AAP PHOTOS)
"There's been some great battles ... I've grown up watching her," said 25-year-old Sabalenka, who owns a 3-1 career head-to-head record over Azarenka.
"It's amazing after giving birth .... it's inspiring me so much and giving me belief that I can have a baby and come back and play at a high level (too).
"Victoria, Serena (Williams), they're really inspiring other girls.
"I saw today she served 16 aces, which is incredible."
Sabalenka has ironed out the misfiring ground strokes and service wobbles that once stunted her big game, and wants to "step in" on more rallies to take it to new heights in 2024.
She has also tried to stay calmer on court, something Azarenka was able to do during an Ostapenko outburst earlier on Friday, the Latvian erupting at the umpire in frustration when down 5-4 in the deciding set.
Jelena Ostapenko debates a call with umpire Julie Kjendlie during her quarter-final loss. (Zain Mohammed/AAP PHOTOS)
"I never want you on my matches ... you ruin my match," the world No.12 told umpire Julie Kjendlie after disputing a double-bounce decision.
Azarenka, currently ranked 21st, said she had prepared for a battle with the 2017 French Open champion.
"With Jelena, sometimes you just have to put on a helmet and try to stay in there," Azarenka said.
"She's an incredible player and a grand slam champion, and she's proved many times she can beat anybody on any given day.
"The quality of tennis was incredible, so to be able to go through ... I'm very proud."
Elena Rybakina eased into the last four in Brisbane after opponent Anastasia Potapova retired hurt. (Zain Mohammed/AAP PHOTOS)
Rybakina had it far easier when Anastasia Potapova retired in their quarter-final after losing the first set 6-1.
Potapova had been receiving treatment for an abdominal injury and eventually conceded after attempting to play on.
Meanwhile, Noskova stopped Russian 16-year-old Mirra Andreeva 7-5 6-3 in the first of what is set to be many WTA battles.
Andreeva, who lost the Australian Open junior final last year, had steamrolled her way to the quarter-finals in scenes reminiscent of world No.40 Noskova's own hot streak to begin 2023.
"I knew it'd be a tough match ... I just wanted to start the right way," Noskova said, forecasting many duels in years to come.
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