Ranieri was axed on Thursday, 298 days after he pulled off one of the most remarkable stories in world sport by leading 5,000-1 outsiders Leicester to the Premier League title.
Even in the precarious world of football management Ranieri's fall from favour was extraordinary and managers expressed their solidarity on Friday.
Mourinho, himself sacked by Chelsea in December 2015 having taken the club to the title the season before, said Ranieri "wrote the most beautiful history" in the Premier League.
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"He deserves the Leicester stadium to be named 'Claudio Ranieri Stadium'," he told reporters, sporting the initials CR on his shirt during his news conference.
"I was sacked as a champion (by Chelsea), a giant negative as I thought - peanuts compared to Claudio. He is paying for his success," he said.
Liverpool manager Juergen Klopp likened Ranieri's sacking to the extraordinary political events of 2016.
"Am I surprised that things like this can happen? No. Not just in football," Klopp, whose side go to Leicester on Monday, told a news conference. "There have been a few strange decisions in 16/17 - Brexit, Trump and Ranieri.
Antonio Conte, whose Chelsea side are favourites to take Leicester's title, added his tribute.
"He reached a dream to win the title, I'm disappointed as a friend and as a coach," he told reporters. "Very, very sad."
Crystal Palace manager Sam Allardyce, who probably expected to be battling Ranieri over relegation, said it was the most surprising dismissal of the season.
"You don't get long these days," Allardyce said.
Leicester have been a shadow of the side that won the title by 10 points last year and five league games in a row left them one point above relegation.
Yet West Bromwich Albion manager Tony Pulis believes Ranieri would have turned Leicester around.
"I'm disappointed," he said. "There's still 13 games to go, they could still have a run of games and finish in mid-table and they could still get through to the next round of the Champions League, which again would be a remarkable season."
Leicester's Thai owners offered Ranieri their "unwavering support" this month and the decision to sack him was described by former Leicester player Gary Lineker as a panic measure.
"I shed a tear last night. I shed a tear for Claudio, for football and for my club. It's inexplicable to me," he said.
"You could explain it in some ways as a panic decision, and for me a wrong decision. It's very sad."
(Reporting by Martyn Herman; Editing by Louise Ireland)
