Brighton produced a stunning comeback at Old Trafford to beat Manchester United 3-2 and knock Michael Carrick's side out of the Carabao Cup.
United looked firmly in control after racing into a two goal lead inside the opening 10 minutes, but Brighton completely turned the game around to book their place in the fourth round.
Shea Lacey gave United the perfect start when the academy graduate scored his first senior goal on his full competitive debut.
Mason Mount then doubled the advantage shortly afterwards, leaving Brighton with a huge task to get back into the tie.
The visitors, however, pulled one back through Charalampos Kostoulas just before half time, giving Fabian Hürzeler's team renewed belief going into the break.
Brighton's momentum continued after the restart.
Pascal Groß equalised with 25 minutes remaining before Maxim De Cuyper completed the remarkable turnaround five minutes later, sending Brighton 3-2 ahead.
United pushed for a response in the closing stages, with Marcus Rashford going close to an equaliser, but Brighton held firm to secure one of their biggest wins of the season.
The defeat also ended a remarkable Manchester United record. It was their first home defeat after leading by two goals at half time since 1984, bringing an extraordinary run of more than 550 home matches to an end.
For Brighton, the victory continues an impressive run against United at Old Trafford and sends them into the Carabao Cup fourth round.
For Carrick, meanwhile, the result makes it two damaging defeats in four days after Sunday's 1-0 Manchester derby loss to City.
United will now have to regroup quickly, with their Premier League campaign becoming the immediate priority.
Man of the Match.... Brighton's comeback was a collective effort, but the second-half goals from Groß and De Cuyper proved decisive in completing the turnaround.