The 29-year-old has become a pivotal figure in the Chelsea backline since joining from Bolton Wanderers in 2012, winning the Champions League, Europa League, Premier League, FA Cup and League Cup in his relatively short time at Stamford Bridge.
His partnership alongside John Terry at the heart of the Chelsea defence was a key component in their run to the Premier League title last season, with the west London club boasting the meanest rearguard in the top flight.
"I’m really pleased to commit my future to Chelsea and it’s great the club has put their faith in me," the centre back, who has made 177 appearances for Chelsea, scoring 15 times, said on the club website.
"I have achieved a lot here and I hope I can keep on learning, helping the team and lifting trophies over the next four years."
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Chelsea have endured a poor start to the season with question marks hanging over their defence that was so watertight in the last campaign.
They are 14th in the table with only 15 points from their opening 14 games of the season and are at home to Bournemouth on Saturday.
(Reporting by Toby Davis; editing by Neville Dalton)
