Victor Moses has signed a two-year contract extension to keep him at Stamford Bridge until 2021, the Premier League leaders have confirmed.
The 26-year-old joined Chelsea from Wigan Athletic in 2012 and spent each of the past three seasons on loan at Liverpool, Stoke City and West Ham respectively.
But he has enjoyed a breakthrough campaign under Antonio Conte this time around after being successfully redeployed to right wing-back.
His first start in what was an unfamiliar role came in a 2-0 victory at Hull City in October - a result that began a record-equalling run of 13 consecutive wins in the same Premier League season.
Moses has made 25 top-flight appearances this term, scoring three goals.
Speaking to Chelsea's official website, the Nigeria international said: "I feel very excited. I'm delighted to be here for another few years now and to sign a new deal.
"Now it's time to concentrate on the team and keep working hard to make sure we win games and try to win the Premier League this season.
"We're having a great season, I'm enjoying my football and we have a good manager here that has given every single one of us confidence. I just want to keep on enjoying it and working hard for the team."
Chelsea technical director Michael Emenalo added: "We are extremely pleased Victor has chosen to extend his contract with us. He is enjoying an excellent season and, under Antonio's leadership, has proved to be an important member of the squad.
"This new contract is testament to Victor's hard work and dedication to succeed at Chelsea and we believe he will be a big part of our future success."
Moses will face one of his former clubs when Chelsea return to Premier League action at West Ham on Monday.
Conte's men currently have a 10-point lead over Tottenham in second.