The young Reds won the trophy last term in thrilling fashion and Paul McGuinness' boys started the defence with a convincing 4-0 win against Torquay United in the previous round, live on MUTV.
The Rams' line-up could feature England youth star Mason Bennett, who made his first-team debut aged 15 this season, and Will Hughes, who has also been selected by Nigel Clough for his Championship side. The promising pair helped Derby dispose of Arsenal away from home in the third round, 1-0 after extra time.
The tie at Altrincham's Moss Lane must be played to a conclusion on the night with extra time and penalties if required.
FA Youth Cup fourth round
Wednesday 18 January 2012
Manchester United v Derby County
Moss Lane, Altrincham
Kick off: 19:00 GMT
Admission prices: £3 adults, £1 concessions