Bruno Fernandes scored his 2nd United penalty in a week after Simon Deli was sent off for a ludicrous handball to block Daniel James’ shot.
The Portuguese, who was at the centre of everything, had a hand in the 2nd as he lifted a pass over the top to Juan Mata, who squared for full debutant Ighalo to smash in from six yards.
And Scott McTominay, making his first start following an injury, side-footed in a third to wrap the tie up before half-time.
Fred scored his first two goals of the season in the last 10 minutes as United acquired the massive scoreline their performance deserved.
Club Bruges delivered hundreds of noisy fans to Old Trafford to assist with a good atmosphere – however their players could not match their efforts and created nothing of note.
The draw for the last sixteen takes place on Friday at 12:00 GMT – with United able to face any of the different teams left.