West Ham United signed French centre-back Jean-Clair Todibo from Ligue 1 side Nice on an initial season-long loan, with an option to make the transfer permanent in summer 2025.
The Premier League club announced on Saturday.
The financial details were not disclosed by either side, but British media reported that the buy option is worth around 40 million euros (AED 160.53 million).
The 24-year-old, who has been capped twice for France, started his career at Toulouse before moving to La Liga side Barcelona in 2019. He made 136 appearances for Nice since his 2021 switch.
"This is an amazing opportunity for me, at a club with huge ambition, who want to really make progress under the new head coach," Todibo, who was earlier linked with a move to Italian giants Juventus, said in a statement.
"It feels like the right time to be coming to West Ham, in the heart of London, with an amazing, passionate fan base. I'm so excited to pull on the West Ham shirt and play at the London Stadium in the Premier League."
West Ham, which finished ninth last season, will begin their Premier League campaign at home against Aston Villa on August 17 under new manager Julen Lopetegui.