Hakim Ziyech has signed a five-year contract at Chelsea ahead of his summer move to Stamford Bridge.
The Blues announced earlier this month they had agreed a £33m deal for the highly-rated Ajax starlet, subject to him agreeing personal terms.
The Morocco winger, who will officially join the Blues on July 1, has now put agreed those terms and told Chelsea’s website: “I am delighted and proud to have signed for such a huge club as Chelsea.
“I am looking forward to next season and hope we can achieve great things together.”
Ziyech, who is Frank Lampard’s first signing as Chelsea boss, has laid on more than 20 goals in each of the last three seasons, and scored 49 times for the Dutch side.
He is viewed as a replacement for Eden Hazard, who left for Real Madrid last summer.
Chelsea director Marina Granovskaia added: “We are delighted Hakim will be joining us, 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.”