Match ends, Manchester United 4, Wigan Athletic 0.
Bastian Schweinsteiger marked his first Manchester United start for a year with a goal and an assist in a convincing FA Cup win over Wigan.
Marouane Fellaini got on the end of Schweinsteiger's cross to put the holders in front just before half-time in this fourth-round tie.
Chris Smalling made it 2-0 following a cross from Anthony Martial, who set up Henrikh Mkhitaryan to tap in the third.
Schweinsteiger completed the scoring with an overhead kick from close range.
Wigan, 22nd in the Championship, had stood up well to the 12-time winners before conceding three goals in 24 second-half minutes.
United, who made nine changes to the side that faced Hull in the second leg of their EFL Cup semi-final on Thursday, sent on substitute keeper Joel Pereira, 20, and defender Axel Tuanzebe, 19, for their debuts.
- Reaction from Old Trafford and Sunday's other FA Cup ties
- FA Cup fifth round draw on BBC One on Monday at approximately 19:20 GMT
Has Schweinsteiger got a United future?
This was an opportunity for a number of United players to prove a point to Mourinho and, after a slow start, they responded with a professional performance as they swept aside the 2013 winners.
Schweinsteiger made his first start since 9 January 2016, Luke Shaw started for the first time since 30 November and Martial had a chance to show he has a long-term future at Old Trafford.
Martial struggled to impose himself up front before he was moved out wide and chipped in with two assists.
Midfielder Schweinsteiger was training with the Under-23 side not long ago but has battled his way back into Mourinho's starting plans.
The former Germany captain, 32, has been linked with clubs in the USA yet his second half display suggested he has not given up on his Old Trafford career.
Wigan left to focus on survival
Wigan, managed by former United reserve boss Warren Joyce, started well at Old Trafford with Callum Connelly and Max Power forcing early saves from Sergio Romero.
But once Fellaini rose above Connelly to nod United in front just before half-time, the visitors looked unlikely to turn the game round.
Romero denied David Perkins before Smalling took advantage of poor marking to meet Martial's cross and make it 2-0.
United's third came when a Wigan corner was cleared by Schweinsteiger to Rooney on the halfway line, who laid it off into the path of Mkhitaryan. He freed Martial, who in return teed up the Armenian to finish from close range.
Schweinsteiger's fourth completed Wigan's misery although their disappointment will be mitigated by a big pay day.
Manchester United manager Jose Mourinho: "We deserved to win. The first half wasn't very good but we managed to lead 1-0 when we needed to play better.
"We knew they would be organised and play with aggression, would be very compact, and to break that down we needed to change a few things.
"The second half was much better. We deserved to win, the job is done and we are in the last 16. Overall I am happy with what we did."
Wigan manager Warren Joyce: " The game plan was working, so we are disappointed to lose. We had good chances, the best chances really, certainly up to half-time.
"The timing of the first goal was unfortunate, then straight after the break we concede another poor goal. It was bread-and-butter stuff - we deal with those balls week in week out, two headers at the back post.
"After that you can forget about the game; we were just chasing and were opening up. The only emotion is disappointment."
Why Fellaini's a hit in the cups - the stats
- Marouane Fellaini has scored six goals in 33 games in cup competitions for Manchester United, compared to seven in 78 league games.
- Fellaini's last four goals for United have come in cup competitions.
- Man Utd have scored four or more goals in a game six times under Jose Mourinho (36 games), two more than they did in 103 games under Louis van Gaal.
- Anthony Martial has been involved in nine goals in his past eight FA Cup games (three goals, six assists).
- Bastian Schweinsteiger claimed his first assist since August 2015 (v Club Brugge), only his second in a United shirt.
- In fact, Schweinsteiger both scored (one) and assisted (one) as many goals in this game as he had in his previous 33 for United.
'We aim to win this beautiful trophy'
- 20RomeroSubstituted forCastro Pereiraat 80'minutes
- 24Fosu-MensahSubstituted forTuanzebeat 68'minutes
- 27FellainiSubstituted forHerreraat 70'minutes
- 40Castro Pereira
- 33BurnBooked at 55mins
- 16MacDonaldSubstituted forBrowneat 76'minutes
- 4PerkinsSubstituted forWildschutat 59'minutes
- 9GriggSubstituted forTunnicliffeat 71'minutes
- Neil Swarbrick
- Shots on Target
Second Half ends, Manchester United 4, Wigan Athletic 0.
Foul by Bastian Schweinsteiger (Manchester United).
Jake Buxton (Wigan Athletic) wins a free kick in the defensive half.
Corner, Manchester United. Conceded by Callum Connolly.
Attempt missed. Ander Herrera (Manchester United) right footed shot from outside the box misses to the left. Assisted by Henrikh Mkhitaryan.
Attempt saved. Ryan Tunnicliffe (Wigan Athletic) right footed shot from outside the box is saved in the bottom right corner. Assisted by Stephen Warnock.
Anthony Martial (Manchester United) wins a free kick in the attacking half.
Foul by Callum Connolly (Wigan Athletic).
Goal! Manchester United 4, Wigan Athletic 0. Bastian Schweinsteiger (Manchester United) right footed shot from very close range to the bottom right corner. Assisted by Ander Herrera with a headed pass following a corner.
Substitution, Manchester United. Joel Pereira replaces Sergio Romero.
Corner, Manchester United. Conceded by Dan Burn.
Attempt missed. Anthony Martial (Manchester United) header from the right side of the box misses to the left. Assisted by Luke Shaw with a cross.
Foul by Anthony Martial (Manchester United).
Michael Jacobs (Wigan Athletic) wins a free kick in the defensive half.
Corner, Wigan Athletic. Conceded by Chris Smalling.
Attempt blocked. Marcus Browne (Wigan Athletic) right footed shot from the centre of the box is blocked.
Substitution, Wigan Athletic. Marcus Browne replaces Shaun MacDonald.
Offside, Manchester United. Anthony Martial tries a through ball, but Juan Mata is caught offside.
Goal! Manchester United 3, Wigan Athletic 0. Henrikh Mkhitaryan (Manchester United) right footed shot from very close range to the bottom left corner. Assisted by Anthony Martial following a fast break.