The Argentine resigned from Southampton after 18 months with the club.
The 42-year-old becomes Tottenham’s 10th manager since 2001 and replaces Tim Sherwood who was sacked on 13 May.
“This is a club with tremendous history and prestige and I am honoured to have been given this opportunity to be its head coach,” Pochettino told the Spurs website.
Pochettino’s assistant Jesus Perez, first team coach Miguel D’Agostino and goalkeeping coach Toni Jimenez have also left Southampton to join him at Spurs.
The White Hart Lane club started last season with Andre Villas-Boas as manager but sacked him in December.
Sherwood replaced the Portuguese and led the club to a sixth place finish in the top-flight.
Tottenham also sold forward Gareth Bale to Real Madrid for a world record £85.3m fee last summer as they signed Paulinho, Roberto Soldado, Nacer Chadli, Etienne Capoue, Christian Eriksen, Vlad Chiriches and Erik Lamela.
“There is an abundance of top-class talent at the club and I am looking forward to starting work with the squad,” added Pochettino.
“Tottenham Hotspur has a huge following across the world and I have great admiration for the passion the fans show for this team.
“We are determined to give the supporters the kind of attacking football and success that we are all looking to achieve.”
The former Espanyol boss took over at Southampton in January 2013, when he replaced Nigel Adkins, and led them to eighth last season – their highest finish in the Premier League.
Luke Shaw, Adam Lallana, Rickie Lambert and Jay Rodriguez all earned their first England caps under Pochettino as the club secured notable wins over Manchester City, Liverpool and Chelsea
Tottenham had been linked with bringing in Ajax coach Frank de Boer as their new manager but have instead opted for Pochettino.
Mauricio Pochettino will need time at Tottenham says David Ginola
Spurs chairman Daniel Levy said: “He has a proven ability to develop each player as an individual, whilst building great team spirit and a winning mentality.”
Former Tottenham winger David Ginola said Pochettino will need to be given time to succeed at the club, while ex-Spurs boss Terry Venables said he was happy with the appointment.
“I think he looks like a very educated guy as far as football is concerned,” Venables told BBC Sport.
“He did a really good job at Southampton. From what I know and what I see of his team, I think that he will be good for Tottenham.”
Pochettino’s future at St Mary’s had been in question, following the departure of chairman Nicola Cortese in January.
Some of the early frontrunners to replace the Argentine at the south-coast outfit include ex-Celtic manager Neil Lennon, former Cardiff boss Malky Mackay, Derby’s Steve McClaren, former Basel boss Murat Yakin and ex-Swansea manager Michael Laudrup.
Southampton chairman Ralph Krueger said: “We will be looking for a manager that shares our values, our principles and our philosophy; a manager who can continue to grow the first team.”
Pochettino described his 18 months at Southampton as an “incredible journey” and wished the club the best for the future
“I hope the team can continue to prosper,” he wrote in a letter on the Saints website.
Born 2 March 1972 in Santa Fe
Played for Newell’s Old Boys, Espanyol, PSG and Bordeaux
While with Espanyol he won the Copa del Rey twice: 1999-2000, 2005-06
Capped 20 times by Argentina, scoring two goals
Fouled Michael Owen to give away penalty during England’s 1-0 World Cup win over Argentina in 2002
Took charge at Espanyol in January 2009
Named Southampton boss on 18 January 2013
Secured notable wins over Manchester City, Liverpool and Chelsea
Prefers to conduct press conferences in his native language of Spanish