Alsonso has been with the Blues since the summer of 2016 and helped them win the Premier League in 2016-17 and claim the FA Cup last season.
The 27-year-old Spain left-back said on Chelsea’s official website on Wednesday: “I am so happy to stay here longer and to keep playing for one of the best teams in the world.
“It’s been a very good two seasons and I am looking forward to more.”
Five more years. 🙌
— Chelsea FC (@ChelseaFC) October 24, 2018
Congratulations on the new contract, @marcosalonso03! 👊 pic.twitter.com/dhtn4fRqDY