Albion out-played, out-fought and out-muscled the once great Manchester United at Old Trafford – and not for the first time.
This was the Seagulls’ third consecutive Premier League win at United’s home ground.
After a moving tribute to Denis Law, the home fans must have wished for his like today as Albion went ahead just five minutes into the match.
Carlos Baleba powered a superb pass from deep in the Albion half into the path of Kaoru Mitoma as he surged towards the United box.
Noussair Mazraoui was thoroughly out-paced and Mitoma selflessly squared for Yankuba Minteh who put Albion in front.
Albion had a couple of half chances to go further ahead – but on 23 minutes there was a mix-up involving Albion keeper Bart Verbruggen and Yasin Ayari and the midfielder felled Amad Diallo.
A split second later, Carlos Baleba pulled down United striker Joshua Zirkzee in the penalty area – and Bruno Fernandes equalised from the spot.
Diogo Dalot had a chance to put United in front but Albion got sufficient numbers back to snuff out the chance.
Albion had further chances to go back ahead before half time, with Minteh finding Danny Welbeck but the former United striker’s effort was blocked by Dalot.
Early in the second half, Minteh and Mitoma set up Baleba who saw his shot hit Harry Maguire and drip to safety.
Albion had the ball in the net on 53 minutes after more great play from Mitoma. Joao Pedro managed to slide under Andre Onana to poke Albion back in front but the goal was disallowed for an infraction by Jan Paul van Hecke.
Zirkzee then had another chance for United but Brighton were ready to counter-attack and steamed forward.
Manual Ugarte cut down Ayari from behind but his late tackle was too late to prevent Brighton from going back in front.
Ayari had managed to play a pass out wide to his right to Minteh who crossed to the far side of the goal for the rapidly advancing Mitoma.
The Japan international hared in and again out-paced Mazraoui, foiling his physical last-ditch attempt by the Moroccan defender.
He was unable to prevent Mitoma from prodding the ball home, putting Albion 2-1 up on the hour.
As Albion controlled the midfield entirely, Antony teed up Zirkzee for another half chance but Van Hecke blocked the effort.
The Dutchman played the ball to Seagulls substitute Solly March, out wide on the right. His deft one-touch pass fell perfectly for the surging Ayari who crossed into the six-yard box.
Onana parried the ball and left the incoming Matthijs de Ligt stranded – right in front of a grateful Georginio Rutter who danced into a shooting position and eased Albion into a 3-1 lead.
With 15 minutes left on the clock, there was no prospect of a repeat of United’s late comeback against Southampton despite efforts from their hat-trick hero Diallo and from Alejandro Garnacho.
Both attempts were blocked by the Albion defence – and Julio Enciso had an opportunity to make it 4-1 before the end.
In stoppage time, Diego Gomez came on to make his Albion debut.
Albion stay ninth in the Premier League, with Manchester United 13th and just 10 points above the relegation places.
Next Saturday (25 January) Albion host Everton at the Amex.
