Garbine Muguruza's power was too much for Paula Badosa in Mexico as she became the first Spaniard in 28 years to reach the final of the WTA Finals.
The two-time Grand Slam champion played with high intensity throughout the 6-3 6-3 semi-final win over her compatriot.
The 28-year-old will now have the chance to become the first Spanish winner of the season-ending tournament.
Standing in her way are Anett Kontaveit or Maria Sakkari, who meet in the day's other semi-final (01:30 BST Wednesday).
Tuesday's encounter in Guadalajara was a first meeting between Badosa and Muguruza, who broke in the third game of the opening set and never looked back.