Match ends, Newcastle United 0, Manchester United 2.
Substitute Romelu Lukaku scored with his first touch as Manchester United beat Newcastle United with Ole Gunnar Solskjaer becoming the second manager in the club's history to win his first four league games in charge.
The Norwegian emulates the feat of Sir Matt Busby in 1946.
Lukaku, who had only been on the pitch 38 seconds, pounced on an error by Martin Dubravka with the Slovakia keeper spilling a free-kick by Marcus Rashford.
Rashford doubled the lead after a sweeping move involving Lukaku and Alexis Sanchez as Newcastle lost for the eighth time at home in the league this season.
Newcastle's best chance fell to Ayoze Perez when the Spanish forward got behind the visitors' defence but Luke Shaw made a last-ditch challenge.
The hosts were fortunate to finish the game with 11 players after substitute Jonjo Shelvey's reckless challenge from behind on Paul Pogba, which went unpunished.
- Solskjaer 'does not want to leave' in summer
- Listen to the Football Daily podcast
- Reaction from St James' Park and the rest of Wednesday's Premier League games
Man Utd go from strength to strength under Solskjaer
After convincing wins over Cardiff, Huddersfield and Bournemouth, this was Manchester United's sternest test under Solskjaer.
They lost the corresponding fixture last season 1-0 but came through this examination while keeping a first clean sheet in eight top-flight matches.
This was another high-octane, attacking performance from a team that has come alive under the caretaker manager.
Although he failed to find the net after scoring four in his previous two games, Pogba was once again influential and typified the new-found belief surging through the team.
Seven of United's previous 12 goals under Solskjaer's reign had been scored in the first half yet they had to wait until the 64th minute to find the breakthrough.
Lukaku made it two goals in as many games after Dubravka failed to hold Rashford's free-kick.
There was little the Newcastle keeper could do about the second goal, Rashford rounding off a delicious move to notch his third goal in four games under Solskjaer.
More blanks for Newcastle
Newcastle played their part in an entertaining game and had chances to score, yet failed to do so for the ninth league game this season.
That his side have only managed 15 top-flight goals will be a huge concern for boss Rafael Benitez, particularly after peppering Manchester United's goal with 14 shots only to draw another blank.
Christian Atsu caused the opposition defence untold problems in the first half but was let down by his finishing.
Atsu also drew one the biggest cheers of the night when he nutmegged Pogba on the edge of his own box.
Shelvey's foul on Pogba was a big talking point but referee Andre Marriner took no action against the midfielder who needlessly clattered into the back of his opponent at speed.
Newcastle worked hard and were organised - but were also limited.
Benitez's side are two points above the relegation zone, with three of their next four league games away to Chelsea on 12 January, home to Manchester City on 29 January and away at Tottenham on 2 February.
"Newcastle could be in a relegation battle come the end of the season and if they can finish fourth from bottom, I'll be delighted with that," said former Newcastle striker Alan Shearer, who was at the game for BBC Radio 5 live.
Man of the match - Marcus Rashford (Manchester United)
'Mistakes cost us' - reaction
Newcastle manager Rafael Benitez: "We made a mistake for the first goal and then conceded on the counter-attack which happens when you play good players. They punish you.
"We had chances in the first half, you lose 2-0 but we deserved more. If you analyse how we concede it's not clear chances. It's mistakes.
"The final third is the key and that's where you pay big money for players who can make the difference."
Manchester United caretaker manager Ole Gunnar Solskjaer: "You'd be happy with four wins from four - we haven't conceded from open play yet either.
"We were slow in the first half but we controlled the game well, we concentrated and overall it was a very professional performance.
"In a five-minute spell we gave them two or three chances but then we settled down again.
"Marcus Rashford has the Cristiano hit, it swerves everywhere, but I liked his goal today. He calmed himself down, just passed it in. Well done.
"He is only 21, you have to remember that. You need to rattle Paul Pogba at times to get him going, he has been immense for us."
No home comforts - the stats
- Newcastle have lost eight of their 11 home Premier League games this season (W2 D1) - only in 2012-13 (nine) have they lost more at St James' Park in a single campaign in the competition.
- Manchester United have won four consecutive Premier League games for the first time since April 2018.
- Man Utd have won 68 of their 100 Premier League games in January - more than any other team has won in the month.
- Newcastle have picked up just one win in their past eight Premier League matches.
- Marcus Rashford has been directly involved in 10 goals in his past nine matches in all competitions (five goals, five assists).
Newcastle entertain Championship side Blackburn Rovers in the FA Cup third round on Saturday (17:30 GMT) before travelling to Stamford Bridge to face Chelsea in the Premier League on 12 January (17:30).
Manchester United also host Championship opposition in the FA Cup on Saturday in the shape of Reading (12:30) before playing Tottenham at Wembley in the league on 13 January (16:30).
- 5SchärSubstituted forMutoat 81'minutes
- 6LascellesBooked at 28mins
- 17PérezSubstituted forKenedyat 69'minutes
- 10DiaméSubstituted forShelveyat 53'minutes
- 1De Gea
- 25A Valencia
- 2LindelöfBooked at 46mins
- 23ShawBooked at 75mins
- 8MataSubstituted forSánchezat 63'minutes
- 11MartialSubstituted forLukakuat 63'minutes
- 10RashfordSubstituted forLingardat 87'minutes
- Andre Marriner
- Shots on Target
Second Half ends, Newcastle United 0, Manchester United 2.
Foul by Luke Shaw (Manchester United).
Kenedy (Newcastle United) wins a free kick in the defensive half.
Attempt saved. Romelu Lukaku (Manchester United) left footed shot from the centre of the box is saved in the centre of the goal. Assisted by Alexis Sánchez.
Attempt missed. Jonjo Shelvey (Newcastle United) right footed shot from outside the box misses to the left. Assisted by Kenedy.
Attempt missed. Paul Pogba (Manchester United) right footed shot from the right side of the box is close, but misses to the right. Assisted by Jesse Lingard following a fast break.
Attempt blocked. Salomón Rondón (Newcastle United) right footed shot from the centre of the box is blocked. Assisted by Yoshinori Muto.
Corner, Manchester United. Conceded by Jamaal Lascelles.
Attempt blocked. Alexis Sánchez (Manchester United) right footed shot from outside the box is blocked. Assisted by Paul Pogba.
Delay over. They are ready to continue.
Delay in match DeAndre Yedlin (Newcastle United) because of an injury.
Attempt missed. Jonjo Shelvey (Newcastle United) header from the centre of the box is just a bit too high. Assisted by Matt Ritchie with a cross.
Substitution, Manchester United. Jesse Lingard replaces Marcus Rashford.
Delay over. They are ready to continue.
Delay in match Nemanja Matic (Manchester United) because of an injury.
Attempt missed. Matt Ritchie (Newcastle United) left footed shot from the left side of the box misses to the right. Assisted by Jamaal Lascelles following a set piece situation.
Foul by Ander Herrera (Manchester United).
Christian Atsu (Newcastle United) wins a free kick on the left wing.
Foul by Marcus Rashford (Manchester United).