Chelsea sign Dutch defender Hato from Ajax
Hato, who has been capped six times, agreed a seven-year contract with the Premier League club.
The 19-year-old is Chelsea's eighth signing since the end of last season as boss Enzo Maresca strengths his squad to cope with the duel demands of the Premier League and Champions League this term.
"I'm very excited, I'm so happy to be here," said Hato, who can operate in central defence or at left-back.
"I thought a lot about my future and wanted to take the next step in my career. Chelsea is the best place for me to do that so I'm very happy."
Hato joined Ajax's academy from hometown club Sparta Rotterdam in 2018 and signed his first professional contract aged 16 four years later.
He scored four goals in 111 appearances for the Eredivisie giants, with his international debut coming as a substitute against Gibraltar in 2023.
Club World Cup champions Chelsea begin their Premier League campaign at home to Crystal Palace on August 17.
The Blues had signed Jamie Gittens, Liam Delap, Joao Pedro, Mamadou Sarr, Dario Essugo, Estevao Willian and Kendry Paez prior to landing Hato.