Tottenham inflicted a humiliating 6-1 defeat on 10-man Manchester United as Ole Gunnar Solskjaer's side imploded at Old Trafford on Super Sunday.
United made the perfect start when Bruno Fernandes converted a second-minute penalty but found themselves a goal behind when Tanguy Ndombele and Heung-Min Son turned the game around inside a frantic first seven minutes.
Anthony Martial was shown a straight red card for lashing out at Erik Lamela on 28 minutes, and Spurs added salt to United wounds as Harry Kane's first and Son's second saw the hosts concede four goals in the first half of a Premier League for the first time.
Serge Aurier rifled Spurs' fifth early in the second and Kane added a sixth from the penalty spot 10 minutes from time as Jose Mourinho haunted his former club on his second return to Old Trafford.
Spurs climb to fifth in the Premier League - two points behind fourth-place Arsenal - after securing their second win of the campaign, while United drop to an unfamiliar 16th after a performance Sky Sports' Gary Neville labelled "pathetic, absolutely pathetic."
Man Utd: De Gea (4), Wan-Bissaka (3), Bailly (2), Maguire (2), Shaw (2), Matic (3), Pogba (2), Greenwood (4), Fernandes (4), Rashford (4), Martial (2).
Subs: Fred (4), McTominay (4), Van de Beek (5).
Tottenham: Lloris (7), Aurier (9), Sanchez (7), Dier (7), Reguilon (8), Hojbjerg (8), Sissoko (8), Ndombele (8), Lamela (7), Son (9), Kane (9).
Subs: Davies (7), Alli (7), Moura (6).
Man of the Match: Harry Kane.
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How woeful Man Utd imploded against Spurs
United could not have wished to have got off to a better start when Martial was bundled over in the area by Davinson Sanchez inside the opening 30 seconds.
Fernandes made no mistake from 12 yards, slotting the opener past Hugo Lloris, but the wheels came off the encouraging United start no sooner after they had got into motion.
- Eric Bailly replaced Victor Lindelof in Man Utd’s only change from the dramatic 3-2 win at Brighton.
- Harry Kane, Davinson Sanchez and Pierre-Emile Hojbjerg were the only players to retain their places as Spurs made eight changes from the win over Maccabi Haifa.
Ndombele restored parity within two minutes, ramming the ball home after Harry Maguire, Eric Bailly and Luke Shaw had made a hash of clearing the danger.
And United's defensive frailties were exposed on nine minutes when Kane's quick free-kick released Son through on goal, and he lifted a delightful shot over De Gea.
Martial was given his marching orders for striking Lamela in the face, and things took a turn for the worse when Kane added Spurs' third after criminal defending from Bailly surrendered possession.
Worse was still to come, with Son doubling his tally from close range as Spurs became the first visiting side to score four first-half goals at Old Trafford since they did back in 1957.
Solskjaer brought on Scott McTominay and Fred at half-time in a bid to shut up shop, but having set up Son, Aurier got in on the act when he rifled Spurs' fifth within six minutes of the restart.
The United horror show ended just as it had started, with a penalty, as Pogba's clumsy challenge on Ben Davies allowed Kane to score his second and Spurs' sixth to confirm the most sobering of defeats on Manchester United.
Neville: Spiritless, spineless, pathetic
Sky Sports' Gary Neville:
"There is no excuse for those players who were out on that pitch today, they were absolutely pathetic. Their body language was terrible, it was spiritless and spineless.
"It was good United finished third last season, they were on the shoulders of Liverpool and City, but they needed to make sure they got closer. City have spent £150m and Liverpool have strengthened with Thiago and Jota.
"They have pulled away psychologically before the season even started, and the psychological damage of not bringing players in is hampering the current squad."
Evra: United players an 'embarrassment'
Sky Sports' Patrice Evra:
"It's a shambles! What is going on at my club? Every team against Manchester United looks like Real Madrid, Barcelona, Bayern Munich. I really don't want to laugh right now - I'm really angry.
"It's different. I know we talk about the 6-1 [against Manchester City] - it's different. Make sure you realise you're embarrassing the club. Look in the mirror and be honest - you're an embarrassment."
Rashford apology - 'I feel horrible'
Marcus Rashford took to Twitter after the match to apologise to United supporters.
"First and foremost I'm a United fan. This is my club. I'm so proud to wear this shirt but there are no excuses, it's just not good enough and to every single fan around the world that tuned in today, I'm just so sorry.
"You deserve so much better than that. I would have stayed away from social media tonight, but you deserve to hear from me during the highs and the lows, there is no hiding. I feel horrible but I promise you we will do better."
Club captain Harry Maguire echoed Rashford, saying on Instagram: "Today was totally unacceptable, we apologise to the fans, you deserve so much more. There's no excuses.
"One thing for sure is that we will do everything we can to put this right. We're all hurting but this is the start of a long season with everything to play for. We must stick together."
What the managers said…
Man Utd manager Ole Gunnar Solskjaer: "At 2-1 we were still in the game, after the red card everything went wrong. You don't win games by making individual mistakes, errors and a performance like that.
"It is embarrassing, I hold my hand up, it is my fault. It is not Manchester United. It is embarrassing, I hold my hand up, it is my fault. It is not Manchester United.
"It is not about getting players in but who is here. Today is the worst. I can't say any more than that. When you are 2-1 down you are in with a chance, 3-1 down a minute later is hard. At 4-1 down it is about character and personality.
"We had to close their avenues to goal, but we didn't come out with any aggression. There are a lot of wrongs today. We need to look at everything."
Spurs manager Jose Mourinho: "Manchester United doesn't lose many matches, to lose by six is of course not every day. Historical victory but in the end three points and three very important points because we lost five points at home.
"We prepared ourselves very well tactically and also psychologically, the team was ready. So ready that a penalty in the first minute and going 1-0 down did not affect the team at all.
"Some people can say you play against 10 men for a long time which is true but for me it is also true that 11 v 11 we were playing extremely well, we were creating huge problems, we were winning 2-1 and they could not find solutions to control us."
Opta stats - Spurs put Man Utd to the sword
- Manchester United suffered their joint-heaviest defeat in the Premier League - losing by five goals for the fourth time in the competition, and for the first time since October 2011 against Manchester City.
- Manchester United have lost their first two home games of a league campaign for just the fifth time in the club's history, with 1986/87 being the previous occasion they suffered two defeats from two at Old Trafford.
- Harry Kane has been directly involved in nine goals in the Premier League this season (three goals and six assists) - only Thierry Henry in 2004/05 has had a hand in more in the opening four games of a Premier League campaign (10).
- Spurs pair Son Heung-Min and Harry Kane have now combined for 26 Premier League goals; the fifth-most of any duo in the competition's history, and the most of any current pair.
After the international break, Manchester United travel to Newcastle in the Premier League at 3pm on October 17, a day before Spurs host London rivals West Ham on Super Sunday at 4.30pm - live on Sky Sports Premier League.