Match ends, Manchester United 4, Newcastle United 1.
Anthony Martial scored twice as Manchester United came from behind to hammer Newcastle United and move four points off a Champions League place in the table.
Martial cancelled out teenager Matty Longstaff's opener for Newcastle with a near post finish before a deflected shot from outside the penalty area by 18-year-old Mason Greenwood went in off the bar.
Marcus Rashford extended Manchester United's lead further with a header - his 11th Premier League goal of the season - before Martial added the fourth.
The France forward went close to becoming the first Manchester United player to score a Premier League hat-trick since 2013 when his low shot hit a post.
- Man Utd's McTominay sustains knee injury
- Reaction from Old Trafford and Thursday's other Premier League games
- What happened in the Premier League on Thursday?
Martial's good day
If there is one player who symbolises the erratic nature of Manchester United just now, it is Martial.
Occasional flashes of genuine brilliance and some decent overall performances are mixed with others so lacking in purpose it must make executive vice-chairman Ed Woodward wonder whether he was right to resist Jose Mourinho's willingness to sell the Frenchman at the beginning of last season.
Even today, at half-time, one very knowledgeable and experienced United observer continued to state his belief the club would be better off without Martial, despite the fact he had scored.
After the break, Martial's second, a fine finish over Martin Dubravka after a woeful Sean Longstaff back-pass had sent him clean though, represented only the fourth time he had scored more than once for United in the league since he was signed by Louis van Gaal in 2015.
He remains a crowd favourite and the ovation he received as he made his way to the dressing room after being replaced by Juan Mata midway through the second half was impressive.
It remains the case that until Martial's goal output improves, he will not be delivering what United require. His tally of nine goals for the season so far is only three short of his best return since his debut campaign, when he scored 17.
Man Utd's Boxing Day glee
If Manchester United could extend their Boxing Day home record across the entire season, they wouldn't be experiencing the kind of drift that has affected them in the post-Sir Alex Ferguson era.
Their record since a 3-0 defeat by Liverpool on 26 December 1978 now reads an impressive 16 wins and three draws from 19 fixtures.
United have not had a Boxing Day win as big as this one since they put five past Wigan on 26 December 2011 - which, ironically, was the last day Newcastle won a Boxing Day away fixture, at Burnley.
That Wigan game is the last time United scored five at home in a Premier League game.
Longstaff loves playing Man Utd
Few players can have had a start to their Premier League careers quite like Matty Longstaff.
The 19-year-old was making his debut when he scored the winner in the reverse fixture at St James' Park in October.
Longstaff kept his place for two more games before he was dropped - and did not reappear until his team met United again. He duly scored again.
Longstaff's shot into the bottom corner from Joelinton's lay-off meant Newcastle had taken the lead at Old Trafford for three seasons in a row - an effort that has brought them no points.
Manager Steve Bruce remains without a win at the stadium where he enjoyed so much success as a player.
Consequently, Newcastle are yet to record a league double over United since 1931.
Man of the match - Anthony Martial (Man Utd)
'Greenwood two years off his best' - what they said
Manchester United manager Ole Gunnar Solskjaer: "We're not going to see the best of Mason [Greenwood] for a couple of years. He's learning, growing as a human being, he'll grow more and more.
"Marcus [Rashford] sprung on the scene the same age and you see more maturity in his game.
"You saw the intent straight away. Newcastle made mistakes but we made them make them by pressing and we made it hard for them."
Newcastle manager Steve Bruce: "We gifted it to them. That is the biggest disappointment we all feel. You can't make that many mistakes here. It is disappointing. The reason we have got a few results is the way we have defended. We made far too many individual errors today.
"You are never surprised about the character of Manchester United. That is the disappointment. No player wants to make the mistakes we did."
Teenage kicks - the stats
- Man Utd forward Mason Greenwood has scored eight goals in all competitions this season - the only teenager with more in Europe's big five leagues is Borussia Dortmund's England forward Jadon Sancho (12).
- Greenwood is just the fourth teenager to score in consecutive home matches for the Red Devils in the Premier League, after Ryan Giggs (1993), Wayne Rooney (2005) and Federico Macheda (2010).
- Newcastle's Matty Longstaff is the third player to score both of his first two Premier League goals in two separate appearances against Manchester United, after Freddie Ljungberg in 1999 and Leighton Baines in 2006.
- Scott McTominay's booking for Man Utd after just 24 seconds is the fastest yellow card given in a Premier League match since exact time data has been collected for bookings in the competition (2006-07).
- Man Utd's Anthony Martial has scored in each of his three Premier League appearances against Newcastle at Old Trafford (4 goals in total).
- Marcus Rashford has netted 15 goals this season in 25 appearances in all competitions, already his best haul for the Red Devils in a single campaign.
Both teams are back in action on Saturday. While Manchester United make the short trip to Burnley (19:45 GMT), Newcastle host Everton (15:00 GMT).
- 1de Gea
- 39McTominayBooked at 1minsSubstituted forPogbaat 45'minutes
- 15PereiraBooked at 35mins
- 10RashfordSubstituted forLingardat 63'minutes
- 9MartialSubstituted forMataat 67'minutes
- 5SchärBooked at 38minsSubstituted forKrafthat 88'minutes
- 43M Longstaff
- 36S Longstaff
- 24AlmirónSubstituted forYedlinat 63'minutesBooked at 81mins
- 12GayleSubstituted forAtsuat 59'minutes
- Kevin Friend
- Shots on Target
Second Half ends, Manchester United 4, Newcastle United 1.
Attempt missed. Fred (Manchester United) left footed shot from outside the box is too high. Assisted by Mason Greenwood.
Substitution, Newcastle United. Emil Krafth replaces Fabian Schär.
Foul by Jesse Lingard (Manchester United).
Florian Lejeune (Newcastle United) wins a free kick in the defensive half.
Andreas Pereira (Manchester United) wins a free kick in the attacking half.
Foul by Christian Atsu (Newcastle United).
Attempt saved. Luke Shaw (Manchester United) left footed shot from the left side of the box is saved in the top centre of the goal. Assisted by Paul Pogba.
Offside, Newcastle United. Jetro Willems tries a through ball, but Joelinton is caught offside.
Foul by Mason Greenwood (Manchester United).
Matthew Longstaff (Newcastle United) wins a free kick in the defensive half.
DeAndre Yedlin (Newcastle United) is shown the yellow card for a bad foul.
Foul by Jesse Lingard (Manchester United).
DeAndre Yedlin (Newcastle United) wins a free kick in the defensive half.
Attempt saved. Paul Pogba (Manchester United) right footed shot from the centre of the box is saved in the centre of the goal. Assisted by Juan Mata with a through ball.
Attempt blocked. Luke Shaw (Manchester United) left footed shot from outside the box is blocked. Assisted by Jesse Lingard.
Attempt saved. Harry Maguire (Manchester United) right footed shot from outside the box is saved in the top left corner. Assisted by Andreas Pereira.
Attempt missed. Sean Longstaff (Newcastle United) right footed shot from outside the box is too high. Assisted by Christian Atsu.
Attempt missed. Federico Fernández (Newcastle United) right footed shot from the left side of the six yard box misses to the left. Assisted by Sean Longstaff with a cross following a set piece situation.