Jose Mourinho has been appointed as Chelsea manager for a second time, the English Premier League club confirmed on Monday.
Following weeks of speculation, the 50-year-old Portuguese has signed a four-year contract with the club he previously coached between 2004 and 2007.
"I am delighted to welcome Jose back to Chelsea. His continued success, drive and ambition made him the outstanding candidate," said chief executive Ron Gourlay in a statement published on the Chelsea website.
"It is our aim to keep the club moving forward to achieve greater success in the future and Jose is our number one choice as we believe he is the right manager to do just that.
"He was and remains a hugely popular figure at the club and everyone here looks forward to working with him again."
Mourinho arrives from Real Madrid, where an initially fruitful three-year spell ended in acrimony following an unsuccessful league title defence, a semi-final exit in the Champions League, and the alienation of senior players including goalkeeper Iker Casillas.
Prior to joining Madrid, he enjoyed a stunning two-season stint at Inter Milan that culminated in an unprecedented sweep of Serie A, Italian Cup and Champions League trophies in 2010.
He succeeds interim manager Rafael Benitez, who led Chelsea to Europa League glory and Champions League qualification this season after replacing the sacked Roberto Di Matteo in November.
Mourinho's first spell as Chelsea manager saw the club emerge as the dominant force in English football.
Backed by the investment of billionaire Russian owner Roman Abramovich, Mourinho won back-to-back Premier League titles in 2005 and 2006, as well as two League Cups and the 2007 FA Cup.
He left in September 2007 after his relationship with Abramovich broke down but the pair soon reconciled and he returns with the objective of turning Chelsea into title challengers once again.
Mourinho has brought coaches Rui Faria, Silvino Louro and Jose Morais with him from Madrid and will be officially presented to the media next Monday.