Chelsea have signed Argentina international Valentin Barco from Ligue 1 side Strasbourg on a seven-year contract, the Premier League club said on Sunday.
Financial details of the deal were not disclosed.
The 22-year-old midfielder was part of the Argentina squad that lost 1-0 to Spain in last month's World Cup final. He spent last season at Strasbourg after the French club made his loan move from Premier League side Brighton & Hove Albion permanent.
"Chelsea FC is pleased to confirm the signing of Argentinian international Valentin Barco from RC Strasbourg," the club said in a statement.
"The versatile midfielder has signed a contract until 2033 and will join up with manager Xabi Alonso and his new team mates later in pre-season."
Barco scored three goals and provided 11 assists in 58 appearances for Strasbourg in all competitions.
The Argentine, who has won five caps and scored twice for his country, began his career at Boca Juniors before joining Brighton in 2024.
Chelsea have strengthened their squad ahead of the new season with the signings of playmaker Morgan Rogers from Aston Villa, defender Maxence Lacroix from Crystal Palace, Atalanta's Marco Palestra and striker Danny Welbeck from Brighton.
Alonso's side, who finished 10th in the Premier League last season, begin the new campaign at Fulham on August 24.