The 25-year-old left United for Real in a world record £80million deal last summer.
“Of course I miss playing for Manchester United,” Ronaldo said in The News of the World.
“I played there for six years and that’s a long time.
“I am still interested in watching Manchester United and, you never know, maybe in the future I could return to play there.
“It’s always possible.”
“I want to fulfil my contract here but, in the future, only God knows,” he added.
“I will not say I am not happy here at Real Madrid.
“I am really happy and everyone knows this is my club but, of course, I miss Manchester United, the boss, the players, because I left family there.”
