Sunderland have agreed a £25.6m fee to sign left-back Dayann Methalie from Toulouse.
The 20-year-old French defender is expected to undergo a medical after a verbal agreement was reached for an initial £23.9m, with a further £1.7m in potential add-ons.
Methalie made 28 appearances for Toulouse in Ligue 1 last season, scoring twice in his final three games, as they finished ninth.
The deal follows a prolonged pursuit by Regis Le Bris’ side as Sunderland look to strengthen their defence before the start of their Premier League campaign at Ipswich Town next Saturday (15:00 BST).
The Black Cats will also compete in Europe for the first time in 53 years and are looking to add greater depth to their squad.
Belgium right-back Thomas Meunier, who signed on a free transfer from Lille, remains the only completed transfer so far in the window for Sunderland.