Chelsea have signed midfielder Mathis Amougou from Saint-Etienne for a fee of about £12m.
The 19-year-old has committed to an eight-year deal and is considered an exciting talent for the future.
He will also boost manager Enzo Maresca's immediate midfield options, after Carney Chukwuemeka departed to Borussia Dortmund on loan and Cesare Casadei joined Torino on a permanent £12.5m deal.
Chelsea also have French top-flight club Strasbourg, to whom they are affiliated, as a potential landing spot for Amougou to develop in future seasons.
"It's an honour for me to sign for such a big club like Chelsea," Amougou said.