Mourinho was sacked by Fenerbahce last month after failing to qualify for the Champions League against Benfica, but he now replaces Bruno Lage in the hot seat. 

The 62 year-old has put pen to paper on a contract that will run until the summer of 2027, with his first fixture against Avs Futebol Sad in the Primeira Liga this Saturday. 

Lage was removed from his post after Benfica started its Champions League campaign with a defeat to Qarabag, which recorded their first-ever win in the competition.

Mourinho started his managerial career with Benfica, but only took charge of nine games before leaving after a dispute with the club president.

He last coached a side in Portugal in 2004, leading Porto to six trophies, including the 2003-2004 Champions League, before joining Chelsea that summer.

After being unveiled as the club's new manager, Mourinho expressed his desire to continue in the role beyond his current contract. 

"As a representative of the millions of Benfica fans around the world, I can tell you that none of the other giants I've had the opportunity to coach have made me feel more honoured or more responsible and motivated than being Benfica's coach," Mourinho said at his first press conference.

"Words are sometimes carried away by the wind, but actions aren't. The promise is very clear: I will live for Benfica, live for my mission.

"I want to work at Benfica, but I want people to trust me, to be on the same page as me. My desire is to successfully complete the two-year contract with Benfica, and for that success to allow the club to renew it sooner or later.

"My goal is to be successful. And at Benfica, success, especially at the national level, means winning competitions."

After leaving Benfica in dramatic fashion almost 25 years ago, Mourinho acknowledged that not all fans will be happy with his appointment.

However, the former Chelsea, Manchester United and Tottenham boss is only focused on bringing success to the club.

"Surely you have some more difficult question hidden, whether I feel that all Benfica fans are happy to be here," he said. "I don't think so.

"Who is magnanimous, who has the power to have everyone by their side, happy, admiring? I don't think anyone.

"I don't feel that way at all, but I do feel a responsibility and motivation to do good things. And here we know what it means to do good things, especially at the national level, to win titles."

Mourinho returns to Stamford Bridge to face former club Chelsea in the Champions League on 30 September.