Latvia's Jelena Ostapenko became the first unseeded woman to reach the French Open final in 34 years by beating Timea Bacsinszky.
The 20-year-old defeated the Swiss 7-6 (7-4) 3-6 6-3 on Thursday to stay on course for a first WTA title.
Mimi Jausovec was the last unseeded player to reach the French Open final in 1983, losing to Chris Evert.
Ostapenko will play either Czech world number three Karolina Pliskova or Romania's Simona Halep on Saturday.
World number 47 Ostapenko, who turned 20 on the day of her victory, edged a first-set tiebreak but looked to have lost her way in the second set when she lost four games in a row.