Fonseca now faces Cech youngster Jakub Mensik in a quarter-final clash between two of the tournament's rising stars.
Brazilian teenager Joao Fonseca continued his remarkable French Open run by reaching the quarter-finals with a four-set victory over Casper Ruud in Paris.
Just two days after knocking out Novak Djokovic, the 19-year-old produced another fearless display to defeat the experienced Norwegian and book a place in the last eigh.
Fonseca now faces Cech youngster Jakub Mensik in a quarter-final clash between two of the tournament's rising stars.
Elsewhere, Spain's Rafael Jodar also advanced to the last eight after fighting back from two sets down to beat compatriot Pablo Carreno Busta, while Alexander Zverev moved through in straight sets and remains among the favourites for the title.

Man City Complete Domestic Double With FA Cup Triumph
Ireland Captain McCabe Linked With Chelsea Switch
Kildare's Walsh Scores Career-Best Finish On LPGA Classic
Monday Morning Sports Update
Kildare Duo Shine As Leinster Cruise Into URC Semi-Finals
PSG Retain Champions League After Shoot-Out Drama
Munster's URC Campaign Ends In Pretoria
Power Slips Down Leaderboard At Charles Schwab Challenge