Chelsea's new owner Todd Boehly promised to build on the team's "remarkable history of success" after the American completed his takeover of the Premier League club on Monday.
Boehly's consortium agreed a deal to buy Chelsea from Roman Abramovich for £4.25 billion on 7 May and the sale has now been officially rubber-stamped.
"We are honoured to become the new custodians of Chelsea Football Club. We're all in, 100 per cent, every minute of every match," Boehly told Chelsea's website.
Boehly's takeover ends Abramovich's 19-year reign as Chelsea owner after the Russian put the club up for sale in March.
Abramovich was sanctioned by the British government for his alleged links to Russian President Vladimir Putin following the invasion of Ukraine.
Los Angeles Dodgers co-owner Boehly has set his sights on emulating Chelsea's success during the Abramovich era, which included five Premier League titles and two Champions League crowns among 19 major trophies.
"Our vision as owners is clear: we want to make the fans proud," Boehly said."Along with our commitment to developing the youth squad and acquiring the best talent, our plan of action is to invest in the club for the long-term and build on Chelsea's remarkable history of success."
Chelsea had been operating under a special government licence which would have expired on 31 May if Boehly had been unable to seal the purchase.
That would have put Chelsea's future in doubt, but they are now able to look forward to next season as the Boehly regime takes the keys to Stamford Bridge.
Boehly's group needed approval from the Premier League, the British government and Portuguese authorities -- Abramovich has Portuguese citizenship -- before the sale could be completed.
"I personally want to thank ministers and officials in the British Government, and the Premier League, for all their work in making this happen," Boehly said.