It comes less than a day after the Blues lost 1-0 to Dinamo Zagreb in the Champions League group stage.
They have had an indifferent start to the league season, losing two of their opening six Premier League fixtures.
In a statement, the club said Tuchel “will rightly have a place in Chelsea’s history after winning the Champions League, the Super Cup and Club World Cup in his time here.”
It added: “As the new ownership group reaches 100 days since taking over the club, and as it continues its hard work to take the club forward, the new owners believe it is the right time to make this transition.
It comes after Tuchel criticised Chelsea’s “huge underperformance” in the Champions League group match, saying his side lacked “hunger and intensity” in the shock 1-0 loss at Dinamo Zagreb.
https://youtu.be/vKrEaV_7o8Y
