Hakim Ziyech has officially signed a five-year deal with Chelsea after agreeing the terms of his arrival from Ajax, the Blues have confirmed.
The Morocco international's move to Stamford Bridge was announced earlier this month after Frank Lampard's side agreed to pay a €40 million (£33.5m/$43.3m) fee to acquire the 26-year-old's services.
Ziyech will spend the rest of the current campaign in the Eredivisie, before making the switch to west London at the close of the season.
"I am delighted and proud to have signed for such a huge club as Chelsea," the attacking midfielder told the club's official website. "I am looking forward to next season and hope we can achieve great things together."
Chelsea director Marina Granovskaia spoke of her elation at tying the playmaker down to a long-term deal at Stamford Bridge, adding: ‘We are delighted Hakim will be joining us in the summer, having been a key target of the club’s in this last window.
"He has consistently been one of the most dangerous attacking players in Europe in recent years, which we saw first-hand in our two games against Ajax in the Champions League.
"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."
A treble winner in the Netherlands last term, Ziyech has topped the Eredivisie's assist charts in the prior three seasons, proving a regular supplier of goals for his club.
He currently tops the same rankings for this season's Champions League with four, despite Ajax having exited the competition at the group stage.
His eye-catching performances on the way to a semi-final exit in last year's tournament saw him named in the Squad of the Season, one of five Ajax players to make the cut.
On the international stage, he was a member of Morocco's squad at both the 2018 World Cup and 2019 Africa Cup of Nations, with his performances at the latter earning him election to the CAF Team of the Year as well.
Ziyech is Chelsea's first major recruit since their transfer ban came to an end earlier this year after it was halved by the Court of Arbitration for Sport.