Azarenka took a 1-6 6-3 6-3 win on Thursday night in New York for a first major win in 11 attempts against Williams.
Williams took a mid-game medical timeout for an Achilles tendon problem in the decision maker’s second game and ended up being broken until 2-0. Unlike her previous three rounds, this time there have been no comebacks for the 38-year-old.
Williams lost her last four Grand Slam finals while trying to equal Margaret Court’s all-time record of 24, but semi-final defeats in the majors are rare. It dropped to 33-6.
Azarenka has reached her first Grand Slam final since losing the 2013 US Open final to Williams.
She will face Naomi Osaka, who beat Grand Slam semi-finalist Jennifer Brady 7-6 (1) 3-6 6-3 in another thrilling match. Osaka won the crown in 2018 by beating Williams in a controversial final.
It’s a rematch of the Western & Southern Open warmup final, which also took place on the US Open website as part of the tournament bubble during the coronavirus pandemic.
Osaka, however, retired with a hamstring injury to deliver the title to Azarenka.
Thursday’s games were played with the roof on at Arthur Ashe Stadium due to rain.