Chelsea have confirmed the signing of teenage midfielder Mathis Amougou from Saint-Etienne on an eight-year contract.

The 19-year-old has moved to the Blues after catching the eye in his 18 appearances in all competitions for the French club this season. Amougou has moved to Stamford Bridge to provide cover and support for fellow midfielders Moises Caicedo and Enzo Fernandez, with Romeo Lavia absent with another injury problem.

The west Londoners have paid Les Verts around £12million for the services of Amougou, whose contract at Stade Geoffroy-Guichard was due to expire in around 18 months' time. "I'm very happy," the Frenchman said in his first interview as a Chelsea player.

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"It's an honour for me to sign for such a big club like Chelsea. They believe in young players and the process they have in place to develop us is fantastic."

Amougou has now been to Cobham for the first time and the midfielder will start training with his teammates in the next few days. The teenager was Chelsea's sole signing of the January transfer window, with the Blues conducting plenty of business with players going out instead.

A total of 17 players departed Chelsea over the course of the window - with Joao Felix's loan move to AC Milan being the final one confirmed on Tuesday afternoon. The majority of the 17 departures were loan deals but a few did leave on a permanent basis - most notably, perhaps, Cesare Casadei, who returned to Italy to join Torino for around £12.5million.