American Coco Gauff defeated world number one Aryna Sabalenka 7-6(4) 6-3 in the semi-finals of the WTA Finals on Friday and will take on China's Zheng Qinwen in the showpiece match.
Sabalenka will end the year at the top of the world rankings but her bid for a maiden WTA Finals title was ended by Gauff who reached her first final at the end-of-season event.
Earlier, seventh seed Zheng overcame battling Czech Barbora Krejcikova 6-3 7-5 to reach Saturday's showpiece on her debut.
It had promised to be a close affair between Sabalenka and world number three Gauff, with the head-to-head record standing at 4-4, and the opening set lived up to expectations.
After trading early breaks, Sabalenka broke again to take a 6-5 lead to serve for the set but Gauff responded, forcing a tiebreak which saw eight breaks of serve over the 11 points.
The American cruised to a 6-1 lead, breaking Sabalenka four times, before the Belarusian broke twice to save the first two set points but Gauff held her nerve to win the first set.
Sabalenka cut a frustrated figure throughout the match and Gauff raced into a 4-1 lead in the second set before the sixth game turned into a marathon affair.
Gauff saved seven break points and at one stage Sabalenka threw her racket into the air but eventually won the game to keep the contest alive. However, the American then broke to love to serve for the match.
Sabalenka rallied and broke again but Gauff kept her cool and, just when it seemed Sabalenka would claw her way back into the tie, the American broke for a fourth time in the second set.
"I'm happy with the way I played, she's world number one for a reason," said Gauff, who can now look forward to Saturday's final against Zheng.