The tennis superstars will play each other Thursday to determine who reaches the women's singles finals
Serena Williams, Naomi Osaka
Serena Williams, Naomi Osaka
| Credit: Jason Heidrich/Icon Sportswire via Getty; Cameron Spencer/Getty

Naomi Osaka and Serena Williams will face off on Thursday in the semifinals of the 2021 Australian Open.

After defeating Taiwan's Hsieh Su-wei in the quarterfinals on Tuesday, Osaka, 23, guaranteed her spot in the women's singles semifinals. Meanwhile, Williams, 39, advanced to the semifinals after she defeated Romania's Simona Halep, who is ranked second in the world, in a 6-3, 6-3 victory.

Whoever wins between Osaka, ranked third, and Williams, No. 10 among female players, will reach the women's singles finals.

"I always watch Serena's matches anyways," Osaka told reporters after she beat Su-wei Tuesday. "Normally I never look at my draw, but everyone's told me about my draw here so I kind of had no choice but to know who my next opponent is. But [it's] definitely going to be really fun."

Osaka and Williams have played each other several times before in tournaments. Osaka won over Williams in the first round of the 2018 Miami Open, and then beat the mom of one in the women's singles final of the 2018 U.S. Open. But Williams struck back when she beat Osaka at the 2019 Rogers Cup.

Osaka's big win over Williams at the 2018 U.S. Open is memorable to many as the match was marred by a verbal altercation between Williams and chair umpire Carlos Ramos. Williams was given three separate on-court violations and later suggested that the umpire's actions were motivated by sexism.

During the post-match trophy ceremony, Williams addressed the crowd, saying, "Well, I don't want to be rude, I don't want to do questions. [Osaka] played well, this is her first Grand Slam. I know you guys were here rooting. Let's make this the best moment we can. Let's not boo anymore. We're gonna get through this and we're gonna be positive. No more booing!"

Fighting back tears after the match, Osaka said, "I know that everybody was cheering for her. I'm sorry it had to end like this. I just want to say thank you for watching the match."

Credit: Tim Clayton/Corbis/Getty Images

Thursday's match against Osaka will be Williams' 40th Grand Slam semifinal. 

Also remaining in the women's singles bracket are Americans Jessica Pegula and Jennifer Brady, and No. 1 ranked Ashleigh Barty of Australia and No. 25 ranked Karolína Muchová of the Czech Republic. The winners of those two matches will advance to the semifinals.

Last year's Australian Open was won by Novak Djokovic in the men's singles and Sofia Kenin in the women's singles.

Tune into the Tennis Channel to watch the match, and for daily coverage of the tournament.