Mason Mount has signed a new Chelsea contract until 2024.
The 20-year-old England U21 midfielder spent last season on loan at Derby under new Blues boss Frank Lampard, where he scored eight goals in 35 games as the Rams reached the Sky Bet Championship play-off final.
Chelsea have now tied down the future of another academy graduate after agreeing a new deal with Ruben Loftus-Cheek to keep him at Stamford Bridge for a further five years earlier this month.
"It's a massively proud moment for myself and my family," Mount told Chelsea's official website
"I joined this club at six years old and it was always my goal to play for the first team one day. I'm really looking forward to the coming season now and working hard to have an impact here at Chelsea.
"I've been at the club for a long time already and hopefully I'll stay for a long time to come."
Chelsea director Marina Granovskaia added: "Mason has come right the way through the Chelsea Academy and has always stood out as a fantastic talent and dedicated individual.
"We have monitored his development extremely closely while he has been out on loan and believe he is now ready to be a member of our squad competing at the top of the Premier League.
"Like another of our Academy graduates, Ruben Loftus-Cheek, we are delighted Mason has committed himself to the club this summer and look forward to an exciting future ahead."
Chelsea are also trying to secure the future of Callum Hudson-Odoi, the 19-year-old England international, who is a key target for Bayern Munich and another product of their academy system.
Hudson-Odoi, who handed in a transfer request at Stamford Bridge in January, is yet to agree terms with Chelsea.