Marcos Alonso has committed his long-term future to Chelsea by signing a contract until 2023.
Since joining the club from Fiorentina in 2016, Alonso has made 92 appearances for the club, scoring 15 goals and providing 11 assists, both as a wing-back and a full-back.
"I am so happy to stay here longer and to keep playing for one of the best teams in the world," Alonso told the club's official website.
"It’s been a very good two seasons and I am looking forward to more."
The 27-year-old has been a key part of the club's recent Premier League title win and their FA Cup triumphs, to the point where he made his Spain debut during his time at the club.
He has since gone on to win three caps for La Roja, having made his bow in March of 2018.