Christian Eriksen scored inside eleven seconds as Spurs became the first side to beat and score past United in 2018 on a dissapointing night at Wembley. The Dane's opener - the second fastest goal in Premier League history - was added to by Phil Jones inadvertent finish into his own net as the Reds slipped to a first defeat in eight games.
Despite this setback, the Reds remain second and three points clear of closest challengers Liverpool and Chelsea - who suffered a shock 3-0 reverse at home to Eddie Howe's Bournemouth side. Manchester City pulled further clear with victory over West Brom with the Reds now locked in a three-way battle for the league's runners up place. Spurs, meanwhile, stay fifth - two points off Antonio Conte's champions, ahead of their trip to Liverpool on Sunday.
Mauricio Pochettino's side, in the thick of the race for the Champions League positions, went ahead when a long ball forward found Dele Alli, he tried to turn but the ball struck Chris Smalling and fell fortuitously into the path of Eriksen who nipped in to score. Technically, the goal should not have stood as replays showed that Harry Kane was two yards inside the United half when the kick-off was taken.
United responded well to that early and unexpected blow, as Jesse Lingard was unable to get his shot away when well placed, and Anthony Martial was thwarted by a superb last ditch challenge from Ben Davies.
Kane, searching for his 100th Premier League goal, fired tamely at David de Gea, but that proved only a temporary reprieve as Spurs maintained their frenetic pace and extended their advantage on the half hour mark. Kieran Trippier's whipped cross caused confusion in the Red backline, and Jones miscued his attempted clearance to instead divert the ball beyond the stranded De Gea and in.
Eriksen, who caused United no end of problems with his surging runs and accurate crossing then flashed a shot wide as Spurs remained a constant threat throughout. Alexis Sanchez, on the periphery for the most part, then had a penalty appeal turned down when his header appeared to hit the arm of Heung - min Son, but referee Andre Marriner remained unmoved.
United had their chances - the best of which fell to Paul Pogba, who headed over and Lukaku, who was denied by a stretching Lloris early in the second half. Marouane Fellaini, who had come on along with Juan Mata in an attempt to turn the Tottenham tide, then had to be replaced through injury only seven minutes after his introduction.
No dramatic turnaround was forthcoming, though, as Spurs beat United in north London for the third successive season to leave the Reds without a win on the road against Spurs since 2011.
Overall team performance: 5/10
United Faithful Man of the Match: Romelu Lukaku. The best of a bad bunch, Rom put a shift in and was unlucky not to score.