Sunderland have reached a £25.6m agreement to sign Toulouse left-back Dayann Methalie.
The 20-year-old Frenchman is expected to undergo a medical after a verbal deal was struck for an initial £23.9m, plus up to £1.7m in add-ons.
Methalie featured 28 times in Ligue 1 for Toulouse last season, scoring twice across his final three matches as they finished ninth.
The move concludes a prolonged pursuit by Regis Le Bris’ side as Sunderland look to shore up their defence ahead of their Premier League opener at Ipswich Town next Saturday (15:00 BST).
The Black Cats are also set for their first European campaign in 53 years and want to add depth to the squad.
Belgium right-back Thomas Meunier, who arrived on a free transfer from Lille, remains the club’s only confirmed signing of the window so far.