Albion almost staged an incredible comeback from three goals down but Bryan Mbeumo’s second of the night – in the sixth minute of injury-time – made sure of the victory.
The hosts were in charge for 73 minutes, with goals from Matheus Cunha, Casemiro and Mbeumo giving Ruben Amorim’s team a three-goal lead.
But Welbeck’s customary goal against his former team – a classy free-kick – gave the Seagulls hope, with 16 minutes of normal time remaining.
With seven minutes added on, you knew there was time for two more goals. Albion got one of those – with substitute Charalampos Kostoulas scoring his first in Brighton colours.
The Greek striker nodded in at the near post from James Milner’s corner – setting up a grandstand finish.
But Mbeumo extinguished any hopes of a sensational comeback with a powerful strike into the roof of the net. It was virtually the last kick of the game.
The match was not without its controversies. There was a big first-half penalty appeal, before the opening goal, when Amad went down under a challenge from Maxim De Cuyper. Play was allowed to continue and it did not impact the hosts’ momentum.
Fabian Hurzeler will no doubt be furious with two controversial decisions against his team, though. Rutter was adamant he was fouled by Luke Shaw in the build-up the third United goal.
And then, referee Anthony Taylor decided not to send Patrick Dorgu off, after he brought down Minteh on the edge of the box – as the Brighton man looked to be through on goal. Albion scored free-kick, anyway, but Hurzeler will argue they should have been up against ten men for the remaining 23 minutes.
The result leaves United fourth in the table, whilst Albion slip to 12th.

1. Manchester United 4-2 Brighton
Manchester United ended a run of three consecutive home defeats against Brighton. Photo: OLI SCARFF/AFP via Getty Images

2. Bart Verbruggen - 7
One of Brighton's better performers. He couldn't have done anything about any of the goals. Made some brilliant saves to keep the scoreline down after far too much sloppiness from his teammates. Vital save at 3-2. Photo: Shaun Botterill/Getty Images

3. Mats Wieffer - 5
Some promising moments going forward but had a really tough night defensively against Man United's lively attackers. Photo: Zohaib Alam - MUFC/Manchester United via Getty Images

4. Jan Paul van Hecke - 6
Intriguing battle against Benjamin Sesko, who didn't get on the scoresheet but caused plenty of problems for Van Hecke. Played a lovely pass to Watson as Brighton piled on the pressure late on. Photo: Zohaib Alam - MUFC/Manchester United via Getty Images
