Sunderland have signed France Under-20 international midfielder Pierre Ekwah from West Ham United on a "long-term" contract, for an undisclosed fee.
The 21-year-old joined West Ham's under-21 side in July 2021, having been part of the Chelsea academy, but did not make a senior appearance.
Before moving to England, Ekwah spent time at the national Clairefontaine academy and at Nantes.
"He is a player we have been monitoring for some time," boss Tony Mowbray said.
"We believe he will add something different to the dynamic of our midfield.
"Having met him, he has a brilliant personality - he wants to get better and show he can play first-team football. He brings a level of physicality and we're really looking forward to working with him."