The Chelsea manager was in charge of Ronaldo at the Bernabeu until this summer, and predicts that his former club would not sell the Portuguese superstar at any price.
“What I know is that Real Madrid is such a rich club that they don’t need to sell and it is such a rich club I think they can ‘eat’ any offer a club can have on Ronaldo,” said Mourinho.
“I know Ronaldo loves Man United and I know he loves the Premier League but I think he is going to stay. It’s just a feeling.”
United sold Ronaldo to Spain in 2009 for a world record fee of £80m, and new manager Carlo Ancelotti has also restated the importance of keeping hold of him. Ronaldo's current deal with the club expires in 2015.
"He is very important for us – I would like him to stay with us," he said, after Ronaldo scored two in a pre-season friendly against Bournemouth.
"“He's a phenomenal player, a great professional," Ancelotti said. "His contract renewal is not my job, but I do not think it'll be a problem.”