Pochettino, who left PSG last year, has signed an initial two-year contract at Chelsea and begins the new role on July 1.
The London club labored to a 12th-place finish in the Premier League this season having struggled under Graham Potter and Frank Lampard, who had been appointed on a caretaker basis.
“Mauricio’s experience, standards of excellence, leadership qualities and character will serve Chelsea Football Club well as we move forward,” co-sporting directors Laurence Stewart and Paul Winstanley said.
“He is a winning coach, who has worked at the highest levels, in multiple leagues and languages. His ethos, tactical approach and commitment to development all made him the exceptional candidate.”
Pochettino guided Tottenham to the Champions League final and won the Ligue 1 title and the Coupe de France with PSG.
The Argentine joins a Chelsea team short on form but with plenty of star power in its ranks after the club spent liberally on signings over the past year.
“The sporting team conducted a diligent and thoughtful process that the Board is proud of,” said owners Todd Boehly, Behdad Eghbali, José E. Feliciano, Mark Walter and Hansjörg Wyss.
“We are delighted that Mauricio will be joining Chelsea. Mauricio is a world-class coach with an outstanding track record. We are all looking forward to having him on board.”
Pochettino’s contract includes an option to extend for a further year. He is Chelsea’s sixth permanent manager since 2018 after Potter, Thomas Tuchel, Lampard, Maurizio Sarri and Antonio Conte.