Karolina Pliskova and Coco Vandeweghe will battle it out for the Porsche Tennis Grand Prix in Stuttgart on Sunday.
Pliskova, the sixth best player in the world, is chasing her 10th WTA Tour title after beating Anett Kontaveit 6-4 6-2 in the semi-finals on Saturday.
The Czech was masterful on her own serve, reclaiming her place at the top of the list of most aces this season, and breezed past her Estonian opponent.
American Vandeweghe is closing in on her third title and first on clay after a 6-4 6-2 win over Frenchwoman Caroline Garcia in the last four.
Pauline Parmentier booked a place in a WTA Tour final for the first time in a decade in Istanbul.
Frenchwoman Parmentier, ranked 122 in the world, beat Irina-Camelia Begu 6-3 6-4 in the semi-final of the Istanbul Cup.
The 32-year-old, who advanced past Caroline Wozniacki in the quarter-final, will now play Polona Hercog.
Hercog beat Greek Maria Sakkari 6-4 6-2 in the other semi-final.