Sakkari defeated Anna Kalinskaya of Russia in the second round on Thursday to win the first set 6-2 and Sakkari was leading 1-0 in the second set before Kalinskaya retired.
Sakkari, who will face Simona Halep in the last eight, continues a successful season where she finished runner-up at the WTA 500 event in Ostrava, Czech Republic and reached the semifinals of the French and US Open majors.
“I am very proud of myself and my team that we have made it to the final for the first time and for the first time in the history of Greece for a female tennis player,” Sakari said.
“I was pretty hard on myself until this year… Growing up, and getting older and more mature, you see some things differently.
“Being good to myself was one of the most important things I’ve changed this year, being good during games and matches.”
World No. 7 Ash is the fifth player after Barty, Arya Sabalenka, Barbora Krajcicova and Karolina Pliskova to qualify for the final, which will take place in Guadalajara, Mexico in November.
The final, contested by the world’s top eight singles players and eight doubles teams, was moved to Shenzhen, China after last year’s event was canceled due to the COVID-19 pandemic.