World number five Stefanos Tsitsipas came from a set down to beat Lorenzo Musetti 4-6, 6-3, 6-0 on Saturday and reach the final of the ATP event in Lyon.
In Sunday's final, the 22-year-old Greek will face either Karen Khachanov or Cameron Norrie who played his way into the semi-finals with a three-set quarter-final win over Arthur Rinderknech on Saturday morning (6-3, 3-6, 6-3).
Musetti, 19, came into the event as an alternate but made the most of his chance with wins over seventh seed Felix Auger-Aliassime, Sebastian Korda and Aljaz Bedene.
The Italian teenager grabbed the first set but Tsitsipas gradually took charge.
Tsitsipas is seeking his second title of the year after winning in Monte Carlo. He also reached the final in Barcelona where he lost to Rafael Nadal.