Romania's Simona Halep moved within one win of a first Grand Slam title and the number one ranking with victory over Karolina Pliskova at the French Open.
Third seed Halep won 6-4 3-6 6-3 to set up a final against unseeded Jelena Ostapenko of Latvia.
Czech second seed Pliskova would have become world number one next week had she won the second semi-final.
Ostapenko celebrated her 20th birthday with a 7-6 (7-4) 3-6 6-3 win over Switzerland's Timea Bacsinszky.
Mimi Jausovec was the last unseeded player to reach the French Open final in 1983, losing to Chris Evert.