Valentín Barco has joined Chelsea from Strasbourg, the London club have announced.
The Argentina international has penned a seven-year deal with the Blues and will join up with the squad later in preseason, the club said.
Barco, who can play at left-back or in midfield, enjoyed a stellar season in France then represented his country at the World Cup where they lost in extra-time of the final to Spain.
Barco played only 19 minutes, against Jordan in the group stage, at the World Cup. However, he notably became embroiled in a feisty incident with England's Jude Bellingham.
Bellingham slapped Barco on the back of his head when Argentina were celebrating their victory over England. Earlier, Barco had run onto the pitch to celebrate an Argentina goal.
Valentin Barco caused a stir at the World Cup against England. Getty Barco, 22, started his career at River Plate then made a handful of Premier League appearances for Brighton & Hove Albion, before briefly playing for Sevilla.
He then moved to Strasbourg -- initially on loan -- where he made a total of 58 appearances, providing three goals and 11 assists.
Chelsea have already signed Morgan Rogers for £117 million from Aston Villa and Marco Palestra for £47m from Atalanta this summer ahead of the new Premier League season.
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Maxence Lacroix, Geovany Quenda, Denner, Danny Welbeck and Dastan Satpaev have also joined Chelsea's ranks, while the club have also brought in Emmanuel Emegha from Strasbourg, who share BlueCo as their owner.
Former Liverpool and England captain Jordan Henderson has also been strongly linked with a move to Stamford Bridge after he reached a mutual agreement with Brentford to terminate his contract.
Xabi Alonso has been brought in as Chelsea manager this season.