The English manager joins his first elite club on the back of a successful spell at Brighton.
Graham Potter has explained his decision to join Chelsea on an open letter to Brighton fans.
Chelsea appointed Potter shortly after their surprise sacking of Thomas Tuchel.
However, their offer convinced Potter to end his three-year spell at Brighton despite his side’s brilliant form.
“This has been three wonderful years with a club that has changed my life. I want to take a moment to say goodbye to all of you who have made it such a special period of my career,” Potter told Brighton’s website.
“I bid farewell to a great club and one that will always mean so much to me and my family. For some I recognise that the change that comes so suddenly in football can be hard to accept. I may not be able to persuade you all to forgive my departure – but I would at least like to take the chance to say thank you.
“I hope that you will understand that at this stage of my career, I felt I had to grasp a new opportunity, I feel I am a better person and a better manager for the experiences I have had here. Not every team selection or decision has been perfect. But the club has created an environment that gives you the scope to make mistakes, learn from them and then improve.”
The former Swansea manager is preparing to face RB Salzburg in his first game in charge of the Blues.