Albion, who are seventh in the Premier League and on track for European qualification, advanced to the last four thanks to their thumping 5-0 quarter-final win against League Two Grimsby Town at the Amex Stadium last month.
Brighton are in fine form at the moment and arrive at Wembley on the back of a 2-1 away win at midtable strugglers Chelsea. Man United however will be a tough test and are currently one of the best teams in the top flight at the moment. Erik ten Hag's men are third in he league and last Sunday enjoyed a comfortable 2-0 win against Nottingham Forest.
Meanwhile, in the other semi-final clash, title-chasing Man City take on Championship promotion hopefuls Sheffield United on the Saturday. A cup run is a huge boast for the fans and also provides healthy income for the club once they reach the later stages of the competition.
Here's the total prizemoney earned so far – looking at each round and how much they stand to win should they reach the final and then lift the trophy...
1.
Brighton and Hove Albion fans will travel to Wembley in force this Sunday for their FA Cup semi-final clash with Man United Photo: GLYN KIRK
2. Middlesbrough 1-5 Brighton
Third round proper winners - £105,000 Photo: Stu Forster
3. Brighton 2-1 Liverpool
Fourth round proper winners - £120,000 Photo: Mike Hewitt
4. Stoke 0-1 Brighton
Fifth round proper winners - £225,000 Photo: Nathan Stirk