Ampadu, who signed from Exeter in 2017 with the fee agreed by tribunal, has impressed since moving to Stamford Bridge.
Ethan Ampadu signs long-term Chelsea deal
Wales international Ethan Ampadu has signed a new five-year contract with Chelsea, the Premier League club announced on Wednesday.
Recommended articles
"I'm really proud and happy, I'm looking forward to the next five years," said the 18-year-old, who can play in defence or midfield.
Ampadu has made seven Chelsea appearances so far and could be involved in Thursday's Europa League clash at PAOK in Greece.
"All I have got to do now is continue to work hard, and hopefully good things will happen," Ampadu said.
Chelsea director Marina Granovskaia said: "Ethan has shown great potential and unbelievable maturity since arriving at Chelsea a year ago.
"In this short time he convinced a lot of people with his exceptional quality and mentality and we look forward to watching him develop into a key player for the club over the coming years."
JOIN OUR PULSE COMMUNITY!
Eyewitness? Submit your stories now via social or:
Email: eyewitness@pulse.com.gh