The 23-year-old's contract also has the option for a further year.
Chalobah has been a key feature of Chelsea's defence since breaking into the first team picture at the start of the 2021/2022 campaign.
The Sierra Leonean-born Englishman has made 43 appearances across all competitions for the Chelsea first team, helping them win the UEFA Super Cup last year and the FIFA Club World Cup earlier this year.
Speaking to the club's official website, Chalobah said: "I'm over the moon to sign this contract. It's been an honour every time I put the shirt on. I want to give my all and do anything for this club.
"As everyone knows I've been here from a young age and to continue here is every kid's dream. Whenever I get the chance, I'll give my all for the club and look for the future ahead.
"I want to say thanks to God for this, without Him none of this would be possible. And just always believing. Thanks to my family as well and the club for trusting in me. I'll now continue to give my all."
Chelsea chairman Todd Boehly and co-controlling owner Behdad Eghbali said: "We're delighted that Trevoh will be extending his stay with Chelsea.
"He has been with us since childhood and has grown into an exceptional young player.
"He's an important part of our men's first team squad and we're excited to see what's next for Trevoh at Chelsea."
