Victor Moses has signed a new deal keeping him at Chelsea until 2021, the club has announced.
The 26-year-old has featured in all but one of the Blues' Premier League games under Antonio Conte this season, contributing three goals and two assists to help his side to a 10-point advantage in the race for the title.
Moses had spent the previous three seasons out on loan at Premier League rivals Liverpool, Stoke City and West Ham United, having moved to Stamford Bridge from Wigan Athletic in 2012.
"I feel very excited," Moses told the club's website. "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's 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's existing deal - worth around £45,000 a week - had been due to expire in 2019.