Chelsea have signed 19-year-old French right-back Malo Gusto from Lyon for 35m euro (£30.7m).
Gusto has signed a deal with the Blues until summer 2030 but will complete the current season at Lyon.
the deal includes 5m euro (£4.4m) in add-ons.
"The defender will now continue his impressive progress on loan [at Lyon] before joining up with the Blues in the summer ahead of the new campaign," Chelsea said in a statement.
Gusto came through the ranks at Lyon before making his first team debut in January 2021.
He has made 15 appearances this season for the French club, who are ninth in Ligue 1.
Lyon said the club "regrets not having been able to keep one of its great hopes trained at the academy" but that they are "happy" Gusto would stay with them for the rest of the 2022-23 season.
Chelsea have signed Noni Madueke,Mykhailo Mudryk,David Datro Fofana, Andrey Santos and Benoit Badiashile on permanent deals in January and have brought in Joao Felix on loan from Atletico Madrid.
The fees for all those deals amount to about £160m and could rise depending on add-ons.