Chelsea will become the fifth club of Pochettino's 14-year managerial career.
Chelsea have appointed former Tottenham and Paris St-Germain boss Mauricio Pochettino as their new manager.
The Argentine, 51, begins his new role on 1 July 2023 on a two-year contract, with an option of a further year.
Interim boss Frank Lampard took Chelsea to 12th in the Premier League - their lowest finish for more than 25 years.
"Mauricio is a world-class coach with an outstanding track record. We are all looking forward to having him on board," the club said in a statement.
Chelsea say Pochettino was first choice and the only manager who was brought into the club for talks.
He will work with sporting directors Paul Winstanley and Lawrence Stewart.
"Mauricio's experience, standards of excellence, leadership qualities and character will serve Chelsea Football Club well as we move forward," Winstanley and Stewart said in a statement.
"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."
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Pochettino is Chelsea's sixth permanent manager in five years following the sacking of Thomas Tuchel and Graham Potter earlier this season, which led to Lampard taking charge on a temporary basis.
He is also the fourth boss of new owner Todd Boehly's reign after the American took over at Stamford Bridge last July.
Chelsea have had a poor season, losing to Manchester City in the third round of both the FA Cup and League Cup.
They also lost to Real Madrid in the quarter-finals of the Champions League, which ended any viable hopes of them qualifying for Europe next season.
From London rival to new head coach
Pochettino had been linked with a return to Tottenham after they parted company with Antonio Conte in March, but he has instead joined his former club's London rivals.
Having started his managerial career with Espanyol before a 16-month spell at Southampton, he then managed Spurs from 2014 to 2019.
The Argentine guided his side to the League Cup final in 2015 and a Premier League runners-up spot in 2016-17, with Spurs missing out on winning both to Chelsea, and the 2019 Champions League final.
He also oversaw an infamous London derby in May 2016 in which Spurs picked up nine yellow cards compared with three for the Blues, the result ending their title hopes for the season.
Following his spell at Tottenham, Pochettino took over from Tuchel at PSG in January 2021.
The French club finished second in Ligue 1 at the end of the 2020-21 seasonbut did win the Coupe de France and the Trophee des Champions, which were the first trophies of Pochettino's managerial career.
More to follow.
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Source: bbc.com