“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!”
Chelsea director Marina Granovskaia added: “Kai is one of the best players of his age in world football, so we are very happy that his future lies at Chelsea.
On a five-year deal, Chelsea confirmed Germany ‘s international Kai Havertz signing.
The 21-year-old attacking midfielder has made the move from Bayer Leverkusen to Stamford Bridge for a fee that will amount to up to £70million, the PA news agency understands.
On Friday, Leverkusen gave Havertz permission to meet with Chelsea, with team bosses from Germany also allowing him to leave the National Team camp.
The contract means Spain’s goalkeeper Kepa Arrizabalaga’s transfer of £72million to Chelsea in 2018 will remain as record signing for the Blues.
The owner of Chelsea, Roman Abramovich, underpinned a remarkable transfer window for the Blues, with manager Lampard endorsing the building of The Blues
“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.”
Prolific German striker Timo Werner, Ajax’s Hakim Ziyech and Leicester’s left-back England Ben Chilwell all made big-money deals to west London.
France Under-21 defender Malang Sarr has a tremendous pledge to have signed a free transfer, but will go out on loan, although Brazil’s stalwart Thiago Silva has arrived from Paris.
Chelsea’s summer investment will rise above £ 200 m should Havertz complete his transition with no problems.
Last summer, the Blues fought through their transfer ban and lost talisman Eden Hazard to Real Madrid, with new boss Lampard impressing at the helm in a demanding first year.
The former England and Chelsea midfielder achieved a fourth-place finish in the Premier League and Champions League qualification in their maiden managerial campaign, and has now gained considerable support for overhauling their Stamford Bridge squad.