Chelsea have announced the signing of Germany international Kai Havertz on a five-year contract.
The 21-year-old attacking midfielder has made the move to Stamford Bridge from Bayer Leverkusen for a fee that will rise to a maximum of £70million, it is understood.
"I am very happy and proud to be here," Havertz told the club's website.
"For me it is a dream come true to play in a big club like Chelsea and I can't wait to meet all the players and the trainers. Yeah, I am very happy to be here!"
Leverkusen gave Havertz permission to meet with Chelsea on Friday, with Germany's team bosses also allowing him to leave the national team camp.
Chelsea director Marina Granovskaia said: "Kai is one of the best players of his age in world football, so we are very happy that his future lies at Chelsea.
"He has proven pedigree in one of the best leagues in Europe, he plays for the German national side and he is an exciting, dynamic talent.
"We are delighted to be able to add his versatility and quality to the squad before the season begins."