A successful two-year spell in Germany followed, where Xhaka helped Leverkusen to their first ever Bundesliga title in 2024.
The deal will take Sunderland’s summer spending to a £114m this summer, albeit having recouped around £37m through the sales of Jobe Bellingham and Tommy Watson.
Only the traditional big six clubs in the Premier League have spent more than the Black Cats after they gained promotion from the Championship through a play-off final win against Sheffield United in May.
Xhaka is set to be the club’s eighth summer signing, following the arrivals of Enzo Le Fee, Habib Diarra, Noah Sadiki, Reinildo Mandava, Chemsdine Talbi and Simon Adingra.