The Blues triggered a release clause in the winger’s contract in January and announced on Sunday evening that they had agreed personal terms with Ziyech over a move to west London.
Frank Lampard is desperate to add more firepower to his squad and he expects to lose the likes of Pedro and Willian this summer ahead of Ziyech’s arrival.
Completing Ziyech’s move was a mere formality but the Blues have now announced that personal terms have been agreed and the 26-year-old took the chance to express his happiness at completing the deal.
‘I am delighted and proud to have signed for such a huge club as Chelsea,’ Ziyech told the club website.
‘I am looking forward to next season and hope we can achieve great things together.’
‘We wish Hakim and Ajax all the best for the rest of the season and look forward to welcoming him to Stamford Bridge in the summer.’