The Blancos star has spoken of his excitement at facing his former club in the Champions League knockout stages, and is looking forward to "going home"
The Portuguese spent six years at Old Trafford, helping Sir Alex Ferguson's men to three Premier League titles before moving to the Spanish capital, and is looking forward to facing his former side.
"On the day of the draw I was out training and I had this strong feeling that we were going to get Manchester United," the 27-year-old told The Sun.
"And when the draw was made I was very happy. It’s a tough match of course - Madrid and United are the two biggest clubs in the world and it’s a real 50-50. It could go either way.
"Manchester was my home and still is in my heart. I love it. Because when people treat you very well you never forget that. And I will never forget United, the people who work there and the supporters.
"So I am so happy to be going back to Manchester."
Ronaldo went on to warn his team-mates of the threat posed by the Red Devils, who are currently 10 points clear at the top of the Premier League, and refused to pick a favourite between Ferguson and Jose Mourinho.
"Manchester United are the best team in England, they are great," he continued.
"And they have a fantastic coach in Ferguson, I know that. But so have we in Mourinho. And he’s my coach now so I obviously hope Mourinho wins!
"It’s like comparing a Ferrari with a Porsche. Both are very good, very experienced and both like to win - and I mean to win everything."
Real Madrid face United at the Santiago Bernabeu in the first leg on February 13 before the return fixture at Old Trafford on March 5.