Unai Emery's clash with Ole Gunnar Solskjaer was the standout tie of the round as the two Premier League giants prepare to face each other again.
The two clubs met nearly four years ago at Old Trafford, with Arsenal emerging as 2-1 winners with the crucial strike from former United forward Danny Welbeck.
Wolverhampton have been rewarded for their shock victory over Liverpool with a fixture against the winner of Stoke City and Shrewsbury Town.
Meanwhile, Chelsea will face off against Sheffield Wednesday or Luton and Tottenham will contest in a London derby with Crystal Palace.
Fourth-round draw in full:
- Swansea v Gillingham
- Wimbledon v West Ham
- Shrewsbury/Stoke v Wolves
- Millwall v Everton
- Brighton v West Brom
- Bristol City v Bolton
- Accrington v Derby/Southampton
- Doncaster v Oldham
- Chelsea v Sheffield Wednesday/Luton
- Newcastle/Blackburn v Watford
- Middlesbrough v Newport
- Manchester City v Burnley
- Barnet v Brentford
- Portsmouth v QPR
- Arsenal v Manchester United
- Crystal Palace v Tottenham