Azarenka recovered from a 6-1 hammering in the first set to win the next two 6-3, 6-3 and schedule her first Grand Slam final appearance in seven years.
The former world number one is enjoying a remarkable run in New York.
"I think when you're coming up from kind of nothing, then you become a number one player in the world, sometimes you can start to think you're invincible and that you're better than everybody, and it's not true," Azarenka said.
Serena Williams falls to Victoria Azarenka in the US Open semifinals
— Bleacher Report (@BleacherReport) September 11, 2020
This is Azarenka’s first win in a major against Serena pic.twitter.com/de4KNgT35O
Nightmare first set for Azarenka
After a first set plagued by double faults and unforced errors, Azarenka turned the tide in the second, upping her service game and getting more returns in play as she began to dictate lengthy rallies.
"I knew I needed to step up with my aggressivity, play a little smarter, play with a little bit more width of the court and bring the intensity up," Azarenka explained.
The two-time Grand Slam winner had never beaten Williams before in a Grand Slam.
Her last appearance in a Grand Slam final came in the US Open in 2013 when Williams beat her.
Serena sets her sights on a Paris rebound
Serena Williams plans to dust herself down after the disappointment of another failed attempt at a record-equalling 24th Grand Slam singles title and continue her chase at the French Open at Roland Garros this month.
When asked on Thursday night whether she would compete for a third title at Roland Garros, she answered: "Yeah, I mean, I'm definitely going to be going to Paris."
