The club said it is "thrilled and delighted" that an agreement was reached for Mourinho to become head coach.
José Mourinho is to be AS Roma coach starting next season, the Serie A club announced on Tuesday.
It comes just a couple of hours after the Italian football club said that head coach Paulo Fonseca is to leave at the end of the current season when his contract comes to an end.
The club said it is "thrilled and delighted" that an agreement was reached for Mourinho to become its head coach.
The Portuguese, sacked last month by Tottenham Hotspur, has signed a three-year contract that will run until June 2024.
"A great champion who has won trophies at every level, José will provide tremendous leadership and experience to our ambitious project," the club said in a statement.
"The appointment of José is a huge step in building a long-term and consistent winning culture throughout our club," it added.
The 58-year-old coach said for his part that "after meeting with the ownership and (General Manager) Tiago Pinto, I immediately understood the full extent of their ambitions for AS Roma."
"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," he said.
Mourinho is one of men's football's most successful coaches having won25 major trophies in his career. He has previously coached Italy's Inter Milan, Britain's Chelsea and Manchester United, Portugal's FC Porto and Spain's Real Madrid.