And, so close are they, that Bale is aware of the Portugal international’s current unhappiness with the club.
But Don Balon say Bale reckons none of Europe’s elite clubs - including United - are interested in snapping up Ronaldo.
The player turns 33 next month.
And any transfer is likely to command a huge fee, despite his advancing years.
PSG are another team being tipped to lure Ronaldo away from the Bernabeu.
FIFA 18: Ronaldo, De Gea and Mbappé pick FUT Team of the Year
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Cristiano Ronaldo to Man Utd: Real Madrid signed star back in 2009
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However, the Ligue 1 giants are unlikely to pursue a deal given they already having Neymar, Kylian Mbappe, Edinson Cavani, Angel Di Maria and Julian Draxler at their disposal.
Meanwhile, Real boss Zinedine Zidane has expressed a desire to keep hold of Ronaldo.
"I just want to talk about his performance and what he can bring to the team on the pitch,” he said.
"Cristiano is a part of this club, where he belongs. The club, the fans, everyone loves him.
"I always say the same thing, I do not see a Madrid without Cristiano. The sporting side is the one that I am interested in. I do not want to talk about the contract and those things."