Real Madrid also confirmed the deal, revealing that the Belgium goalkeeper will put pen to paper on a contract that takes him up to the end of the 2023-4 season.
The Blues broke the world-record fee for a goalkeeper by signing Arrizabalaga, but who exactly is the 23-year-old?
Arrizabalaga has played 53 La Liga matches for Athletic Bilbao since breaking into the team in 2016.
Arrizabalaga, who only signed a new seven-year deal with Athletic in January, becomes Maurizio Sarri's second high profile signing since taking charge, following in the footsteps of midfielder Jorginho, who followed Sarri from Napoli for around £50m.
He was also in the Spain squad for the World Cup in Russian Federation as back-up to David De Gea, but has yet to make his competitive debut for Spain or play in the Champions League.
Malaysia’s ex-PM Najib charged with more corruption counts
His is accused of having received 42m ringgit ($10m; £8m) from state fund 1MDB in his personal bank account. He appeared at the MACC office in Kuala Lumpur on Tuesday after he was summoned by the anti-graft agency.
Illinois Celebrates First Annual 'Barack Obama Day'
I think it's awesome, and I think we should celebrate it", Rauner said while signing the state holiday into law. Moving forward, August 4, the former president's birthday, will be celebrated as " Barack Obama Day".
Ola to launch in Britain as Uber rivalry heats up
Yesterday, the Licensed Taxi Drivers' Association (LTDA) and 11 other organisations in London will be filing a case against Uber. Ola plans to expand its services across Britain, where Uber already has a presence, by the end of the year, the company added.
"It's a very important decision for me, for my career, and also for my personal life", Kepa told Chelsea's website. So, I don't know.
The Blues faced a race against time as to sign the young global before the Premier League transfer window closes on Thursday at 18:00 CEST - tasked with convincing the shot-stopper to move to England, despite Kepa having just renewed his contract.
"Athletic thank the player for his contribution throughout the time he has been at the club".
Courtois only had a year left on his deal and has been absent from training this week as he looked to push through a move before the transfer window ended for Chelsea on Thursday.
The deal that sees Courtois join Real Madrid for a reported £35million sees midfielder Mateo Kovacic head the other way on a season-long loan.
Tottenham defender Toby Alderweireld has been eyeing a move away from the north London club and could be a target for United, who appear to have missed out on Bayern Munich's Jerome Boateng.