Jose Mourinho was appointed Wednesday to replace the sacked Mauricio Pochettino at Tottenham, with a brief to revive the flagging fortunes of a club languishing in the lower reaches of the Premier League.
The former Chelsea, Real Madrid and Manchester United manager has signed a contract until the end of the 2022/23 season.
"I am excited to be joining a club with such a great heritage and such passionate supporters," said Mourinho, who has won domestic league titles in Portugal, England, Italy and Spain.
"The quality in both the squad and the academy excites me. Working with these players is what has attracted me."
Mourinho's glittering CV includes Champions League titles with Porto and Inter Milan.
The 56-year-old also won three Premier League titles over two spells in charge of Chelsea, and returned to England to manage Manchester United in 2016.
"In Jose we have one of the most successful managers in football," said Spurs chairman Daniel Levy. "He has a wealth of experience, can inspire teams and is a great tactician.
"He has won honours at every club he has coached. We believe he will bring energy and belief to the dressing room."
The club tweeted a picture of their new Portuguese boss holding a Spurs shirt ahead of his first match in charge -- a London derby at West Ham United on Saturday.
Mourinho was sacked by Manchester United last December following a poor run and has been without a club since, most recently working as a TV pundit.
He remains a big name but there will be questions over whether his pragmatic style can mesh with Tottenham's tradition of attacking football, a problem he also faced at Old Trafford.
Argentine Pochettino was dismissed on Tuesday, with Spurs struggling in the league after picking up just three wins from 12 games.
The 47-year-old had transformed the club's fortunes since arriving in 2014, and although he failed to win a trophy, he took Spurs to the Champions League final for the first time in their history just six months ago.
But that masked indifferent domestic form in the second half of last season, and Pochettino was unable to reverse the slide in this campaign.
As well as tumbling down the league, they were knocked out of the League Cup by fourth-tier Colchester United and suffered an embarrassing 7-2 defeat at home to Bayern Munich in the Champions League.
Former Tottenham manager Harry Redknapp told the BBC that poor results forced the club's hand.
"I love Mauricio Pochettino, but he has been averaging a point a game over the last 25 games," he said. "The Tottenham board are ruthless businessmen, they will have realised that at this rate they might not make the top four.
"Also the same voice after six years starts to wear a little thin, a new man can find another 10 percent, they will find a spring in their step for Jose's first game."
Tottenham qualified for the Champions League four times under Pochettino, culminating in a dramatic run to the European Cup final in June, which they lost 2-0 to Liverpool in Madrid.
However, domestic results had been on the decline since February, with Spurs clinging on to a top-four finish last season despite winning just three of their final 12 league games.
Mourinho arrives with the club 11 points outside the Premier League top four, though they are well placed to reach the last 16 of the Champions League.
The job done by Pochettino was all the more remarkable given the tight budget for transfers and wages in comparison with Tottenham's Premier League rivals, as the club built a new stadium at a cost of more than £1 billion ($1.3 billion).
Much of Pochettino's success came from nurturing a squad of young players into household names such as Harry Kane, Dele Alli and Christian Eriksen.
A series of Spurs players paid warm tribute to their departing manager.
Tottenham and England forward Kane tweeted: "Gaffer. I'll be forever thankful to you for helping me achieve my dreams."
South Korean forward Son Heung-min said in an Instagram post that "words are powerless to express my gratitude".
The Tottenham Hotspur Supporters' Trust released a statement expressing "concerns" and seeking clarity over how the new boss and the board would work together.
The group asked: "Is the manager solely accountable? How much has the board's line on wages and transfers contributed to player unrest and disaffection?"