Chelsea have agreed personal terms with Ajax winger Hakim Ziyech over a five-year-deal which will see the Morocco international move to Stamford Bridge for 40m euros (£33.3m) in the summer.
An agreement was reached between the clubs earlier this month and the 26-year-old will remain at the Eredivisie leaders for the rest of the season.
“I am proud to have signed for such a huge club as Chelsea,” said Ziyech.
“I am looking forward to next season and hope we can achieve great things.”
Chelsea director Marina Granovskaia added: “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.”
Ziyech has scored nine goals in all competitions for Ajax this season, contributing to three goals as the Dutch side drew 4-4 against Chelsea in the Champions League in November.