He slots into Le Bris' technical group alongside assistants Alessandro Barcherini and Michael Proctor, with Isidre Ramon Madir continuing as chief analyst, James Brayne handling set-pieces and Neil Cutler overseeing the goalkeeping department.
Across a 24-year career, Fonte racked up close to 900 appearances for club and country. English fans will remember him best from his eight years at Southampton, where 288 appearances helped carry the Saints from League One into the top flight, while a stint at Lille brought a Ligue 1 title in 2020-21 and 196 games for the French club. On the international stage he collected 50 Portugal caps and lifted both Euro 2016 and the 2018-19 Nations League.
Director of football Florent Ghisolfi said Fonte's experience would add real value to the club's coaching operation.
"Jose joins our coaching team with a wealth of experience as a player at the top level," Ghisolfi said.
"He will bring that experience, along with tremendous energy, to a technical staff that is already performing outstandingly under the guidance of Regis.
"We believe those qualities, combined with his strong leadership skills, will add great value to our club as we look to push forward both in the Premier League and on the European stage. We're delighted to welcome Jose to Sunderland AFC." Fonte will officially begin his role on 20 July, joining the club as it prepares for its first European campaign in more than 50 years alongside a second season back in the Premier League.
Elsewhere at the Stadium of Light, midfielder Jack Whittaker has signed a new two-year contract after scoring 11 goals and adding four assists across all Under-21 competitions last season, having also been named among the substitutes for Sunderland's Premier League game against Brighton.
"I've been at this club since I was seven years old so I'm really happy to sign and it's a huge step in the right direction," Whittaker said. "Every single coach that I've had has pushed me and given me the right sort of challenges as well as support me so I can't thank them anymore."