Jose Mourinho returned to Manchester United and humiliated his former club as Tottenham came from behind to record a famous Old Trafford win.
Son Heung-min and Harry Kane scored twice, with Tanguy Ndombele and Serge Aurier also on target as 10-man United suffered a defeat on a par with their 6-1 thrashing at home by Manchester City in 2011.
Bruno Fernandes had put the hosts in front through a penalty after Davinson Sanchez barged Martial over inside the box within 30 seconds.
It meant it was not only the heaviest defeat since Ole Gunnar Solskjaer took temporary charge in December 2018, but also the largest United have suffered since Ed Woodward took over as executive vice-chairman in 2013.
The result leaves United 16th in the Premier League, with newly promoted Fulham and West Brom the only clubs with a worse goal difference. Only West Brom have conceded more than their 11 goals.
United were completely outplayed, even before they were reduced to 10 men midway through the first half when Anthony Martial dragged his hand across Erik Lamela’s face in reaction to an elbow in his neck.
In contrast, Tottenham moved up to fifth after emerging from a packed schedule of five games in 11 days in three competitions with a creditable four wins and a draw – their last two games have had five-goal winning margins.
It is also Tottenham’s biggest win at Old Trafford and matches their record home win over United, 6-1 in September 1932.
Earlier, West Ham United had picked up where they left off against Wolves last weekend with another impressive display to end Leicester’s 100% winning start to the season.
Boss David Moyes was again absent from the touchline as he continues to recover from coronavirus, but as in last weekend’s 4-0 victory, it did not hamper the Hammers, who offered an excellent balance of graft and guile.
Michail Antonio scored the first, heading in at the back post from Aaron Cresswell’s pinpoint cross from deep after the striker had himself found his team-mate with a quickly-taken free-kick.
Cresswell also assisted the second, but the credit was due more to a wonderful first touch and calm finish from Pablo Fornals, than the defender’s long ball forward.
But for a solid block from Caglar Soyuncu to repel a Jarrod Bowen shot, and a sliding Jonny Evans intervention to stop the ball finding an unmarked and well-placed Antonio, the Foxes would have been further behind before half-time.
In the second half, the brilliant Declan Rice struck the crossbar with a shot from inside the box following a driving run from deep before Bowen sealed the win with a neat finish after collecting a through-ball from Fornals.
For all their possession and territory, Leicester failed to produce a single shot on target, with their misery compounded when Jamie Vardy was flagged offside to rule out a Harvey Barnes finish in added time.
City remain second in the table, but could lose that spot with Liverpool still to play later on Sunday, while West Ham are up to eighth.
At the Emirates stadium, Arsenal scored two quick-fire team goals to extend Sheffield United’s point-less start to the Premier League season – although the Blades did manage their first goal.
The Gunners did not really get going until the 60th minute when Bukayo Saka celebrated his first England call-up with a header from Hector Bellerin’s cross.
Three minutes later they doubled their lead with Nicolas Pepe’s good run and finish into the bottom corner – finishing off a move with 19 passes.
They looked completely in control until David McGoldrick curled home the Blades’ first league goal of the season.
But it was not enough to affect the outcome and United have now lost seven consecutive top-flight games for the first time since 1975.
Mikel Arteta’s Arsenal move onto six points from three games, having lost 3-1 to champions Liverpool last Monday.
Elsewhere, West Bromwich Albion’s slow start to their premier league return is not about to end as their disappointing start to the season continued with defeat at Southampton.
Moussa Djenepo opened the scoring with a clinical finish for the hosts before Oriol Romeu’s stunning strike sealed a deserved win.
The loss means West Brom have managed to pick up just one point from their first four games on their return to the top flight.
Asked whether it was a tough learning experience coming up from the Championship, Bilic said: “You have to learn, but this is not a school.
“You have to be competitive and do your best. We have to do more and show more determination, and show a better mentality than we have shown.
“Southampton were better in everything. I know the guys want it but there has to be so much more determination and desire.”
The Saints had lost their first two league fixtures of the season but have now recorded back-to-back league wins with this result.
Djenepo’s opener just before half-time, a clinical finish into the bottom corner, was just reward for an excellent first-half display in which only a string of fine saves by Sam Johnstone prevented Southampton from taking the lead earlier.
Johnstone kept out Ryan Bertrand’s curling effort before reacting quickly to prevent Semi Ajayi from diverting the ball into his own net and then stopped Che Adams from pouncing with the follow-up.
The Manchester United academy product dived at full stretch to deny Danny Ings’ header but could do nothing about Djenepo’s smart finish.
West Brom were marginally better after the break but still did not trouble Alex McCarthy enough in the Southampton goal.
The hosts made sure of the points when Romeu superbly volleyed in Stuart Armstrong’s cross for his first goal in 20 months.
Leicester City 0- 3 West Ham United
Southampton 2- 0 West Brom
Arsenal 2- 1 Sheffield United
Wolves 1 -0 Fulham
Man United 1-6 Tottenham
Aston Villa V Liverpool (Late kick-off)