The Portugal captain, 33, was sent off during Juve’s 2-0 win over Valencia last week after appearing to pull defender Jeison Murillo’s hair.
It was the first Champions League red card of Ronaldo’s career. Juventus play United in Group H at Old Trafford on 23 October.
A three-match suspension would have seen Ronaldo also miss the return fixture in Turin on 7 November. He will definitely miss Juve’s next Champions League game against Swiss club Young Boys on 2 October.
Five-time Champions League winner Ronaldo – who joined Juve from Real Madrid for £99.2m in the summer – tried to latch onto a cross when he was blocked off by a tumbling Murillo.
He gesticulated to Murillo to get up and appeared to pull the defender’s hair before turning away in frustration.
Referee Felix Brych consulted his assistant behind the goal before producing a red card, reducing Ronaldo to tears as he left the pitch.
Source: BBC News