The midfielder has signed an eight-year contract and will begin training with his team-mates in the coming days.

'I'm very happy,' Amougou said. '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 made his debut for Saint-Etienne at the start of last season against Nimes and featured in Ligue 2 as the club secured promotion to the French top flight.

The 19-year-old established himself as a regular starter in the Saint-Etienne midfield at the beginning of the current campaign and made 17 appearances in Ligue 1.

On the international stage, Amougou has been capped at several age groups by France. He notably claimed the Bronze Ball for his performances at the 2023 Under-17 World Cup and received his first call-up to the Under-20 squad earlier this season.

Welcome to Chelsea, Mathis.