The local enemies were pulled out of the hat together in this evening's draw following their respective wins in the previous round.
Currently, Pep Guardiola has the edge over his fierce rival Mourinho as he guided his City team to a 2-1 win in the Premier League derby under a fortnight ago, but the Red Devils will be looking for revenge in the week of October 24.
Elsewhere, there will be a London derby in the fourth round as West Ham United have been drawn at home against Antonio Conte's Chelsea, while Arsenal will take on Championship outfit Reading at the Emirates.
Norwich, who knocked out Everton in the third round, avoided Premier League opposition as they face fellow Championship club Leeds United, while Preston North End will take on Newcastle United after booting out Bournemouth.
EFL Cup fourth-round draw in full:
West Ham vs. Chelsea
Manchester United vs. Manchester City
Arsenal vs. Reading
Liverpool vs. Tottenham
Bristol City vs. Hull
Leeds vs. Norwich
Newcastle vs. Preston
Southampton vs. Sunderland