The 27-year-old Senegal international agreed to a four-year deal with the Red and Blacks which will keep him at Roazhon Park until 2023.
[#MercatoSFRC]— Stade Rennais F.C. (@staderennais) August 6, 2019
✍Le @staderennais et le @StadeDeReims ont trouvé un accord pour le transfert définitif d’Édouard #Mendy.
Degemer Mat Édouard ! 🤝
---#AllezRennes#ToutDonner 💪🔴⚫ pic.twitter.com/yoNzATcUrP
Mendy made 78 league appearances during his four-year stay with Reims, including 38 last season to help David Guion’s men finish eighth.
The goalkeeper, who was part of Senegal’s silver-winning squad at the 2019 Africa Cup of Nations, is delighted with the move.
"I am very happy to join the Stade Rennais FC. It is the outcome of the conversation I had with the president,” Mendy told the club website.
“Stade Rennais FC are an ambitious club which is evident with their performances in the Coupe de France and European tournaments.
“Everyone told me good things about the club before my arrival. I was also able to visit the infrastructures which are of an excellent standard. I cannot wait to be part of this adventure."
Mendy started his European career with Cherbourg in 2012 and spent two years with the side before joining Marseille B.
He signed for Reims in 2016 and played a key role as the Red and Whites won the 2017–18 Ligue 2 title and gained promotion to French topflight.
The goalkeeper will link up with his compatriots Ismaila Sarr, Diafra Sakho and M'Baye Niang as well as Ivory Coast’s Souleyman Doumbia and Mali’s Hamari Traore at Rennes.