The Champions League last-16 draw will take place again at 14:00 GMT after a “technical problem” caused an error in the initial one.
Manchester United were initially drawn to face Villarreal but this was not permitted under tournament rules as they had been in the same group.
Instead the La Liga side were paired with Manchester City, while United drew Paris St-Germain.
In a statement, Uefa said the draw had been “declared void”.
It added: “Following a technical problem with the software of an external service provider that instructs the officials as to which teams are eligible to play each other, a material error occurred in the draw for the Uefa Champions League round of 16.
“As a result of this, the draw has been declared void and will be entirely redone at 14:00 GMT.”
A second administrative error saw United excluded from the pot of possible opponents for Atletico Madrid and Liverpool included instead, although United could have played the Spanish side and Liverpool could not, having progressed into the knockout stage from the same group.
Atletico were drawn to face Bayern Munich but following the draw, the La Liga champions said they were in talks with Uefa “to ask for explanations and a solution after the mistakes made”.
European football expert Guillem Balague suggested 13-time champions Real Madrid, drawn against Portuguese club Benfica, “are not pleased at all by what has happened”.