Jose Mourinho will take over as Roma's manager at the end of the current season.
The Portuguese has landed himself another job just 15 days after being sacked by Tottenham.
Roma announced earlier on Tuesday that current manager Paulo Fonseca will leave his position at the end of the season.
Club president Dan Friedkin and vice-president Ryan Friedkin said on the club's official website: "We are thrilled and delighted to welcome Jose Mourinho into the AS Roma family.
"A great champion who has won trophies at every level, Jose will provide tremendous leadership and experience to our ambitious project.
"The appointment of Jose is a huge step in building a long-term and consistent winning culture throughout the club."
Mourinho is one of only three managers to have won the Champions League with two different clubs, a feat he has also repeated in the Europa League.
"When Jose became available, we immediately jumped at the chance to speak with one of the greatest managers of all time," said Roma general manager Tiago Pinto.
"We were blown away by Jose's desire to win and his passion for the game: no matter how many trophies he has won, his primary focus is always on the next one. He possesses the knowledge, experience and leadership to compete at all levels."
Mourinho, who has previously coached Porto, Chelsea, Inter Milan, Real Madrid and Manchester United, was sacked by Spurs last month after 17 months in charge of the North London club.
"After meetings with the ownership and Tiago Pinto, I immediately understood the full extent of their ambitions for AS Roma," Mourinho said.
"It is the same ambition and drive that has always motivated me and together we want to build a winning project over the upcoming years.
"The incredible passion of the Roma fans convinced me to accept the job and I cannot wait to start next season."
Mourinho completed a historic treble with Inter – including the Champions League – in 2009-10 but in a recent interview with The Times said he would not hesitate joining any one of their rivals in the future.
"There is a special affection. But if one day I have to go to Italy and coach a rival club, I don't think twice," he said. "I have this professional way of look to things."
As well as his triumphs with Inter he also won the Champions League with Porto in 2004, three Premier League titles with Chelsea and La Liga with Real Madrid in 2012. He led Manchester United to the Europa League in 2017.
Fonseca's Roma looked to be on course for a top-four finish that would secure Champions League football for next season at the turn of the year, but one win in their last eight league matches has left them seventh in the standings.