The Old Trafford legend says the winger's style is perfectly suited to Sir Alex Ferguson's side, reports The Daily Mirror.
Cantona, who spent six glorious seasons with United before retiring in 1997, said: 'He is still young, and so maybe he wants to take on fresh challenges.
Speaking out: Eric Cantona says Ronaldo should stay at Old Trafford.
'I can understand if this is the reason why he wants to leave for Real.
'But if he were to leave because of something else, he would be doing something absolutely bloody stupid.'
The Frenchman, 42, currently manager of the France Beach Soccer Team, also declared his aim to become United's manager one day.
He said: 'It would be a huge honour for me to become Manchester United's coach - it would be marvellous.'
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