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The deal is reportedly worth £12million, with the defender signing an eight-year contract to keep him at Stamford Bridge through to 2033.

Chelsea is said to have agreed the transfer with partner club Strasbourg back in January, with the move made official on Tuesday.

The 19 year-old joined Strasbourg from Lyon in August 2024, signing a five-year contract.

Sarr made 27 appearances in Ligue 1 last season, helping Strasbourg to a seventh-place finish.

He helped the team keep 10 clean sheets, a team-high along with goalkeeper Djordje Petrovic, while he also made the most blocks (20) across the team. His 25 interceptions were only bettered by three other players.

Sarr will be available for the start of Chelsea's Club World Cup campaign, which begins against Los Angeles FC on 16 June.

Sarr is Chelsea's fourth arrival of the transfer window, after Liam Delap, Estevao and Dario Essugo, with the Blues also reportedly looking to bring in Borussia Dortmund's Jamie Gittens.