Louisa Chirico upset the odds as she came from behind to defeat Annika Beck 5-7 6-2 6-2 and move into round two of the Open de Limoges.
Fourth seed Beck is ranked some 64 places above Chirico in the world rankings and was overwhelming favourite to progress in France.
However, the German was broken nine times in a disjointed display, and Chirico - who had never faced Beck on the WTA Tour - took advantage to win a marathon contest lasting two hours and 15 minutes.
Kristyna Pliskova was a finalist in Limoges in 2013 but her run was ended by the evergreen Francesca Schiavone, the 35-year-old - a French Open winner in 2010 - winning 6-4 6-3.
Tamira Paszek upset Andreea Mitu 6-4 6-3, while Mandy Minella saw off Stefanie Vogele 6-4 6-2.
In other matches, Katerina Siniakova was a 6-4 7-6 (7-1) victor over Alize Lim, while Richel Hogenkamp defeated Oceane Dodin 7-6 (7-5) 7-5.