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.
“There is an abundance of top-class talent at the club and I am looking forward to starting work with the squad,” he added.
“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 place in the Premier League.
His future at St Mary’s had been in question, following the departure of chairman Nicola Cortese in January.
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.”
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.”
Source: BBC