Sunderland have signed the DR Congo youth international Jules Ahoka from Royal Antwerp on a long-term contract. The fee is understood to be in the region of 10m euros (£8.6m).
The 20-year-old midfielder is Sunderland's third summer signing, following the arrivals of the Belgium left-back Thomas Meunier and the France right-back Dayann Methalie.
"I am very happy and proud to join Sunderland," Ahoka said. "It is a big club with great ambitions, and I am excited to be here. I want to work hard, learn from my team-mates and the staff, and continue developing as a player. I will give everything for the club and I cannot wait to get started."
Sunderland's director of football, Florent Ghisolfi, said: "Jules is a player we have been following closely and he has shown some very encouraging qualities for his age. He has huge potential and we believe Sunderland is the right environment for him to continue his development."