Albion's under-23 team have been promoted into Premier League 2 Division 1 after a 2-0 win against Aston Villa this afternoon.
Brighton went into the play-off final in outstanding form, unbeaten in 17 games in normal time, and had beaten League Two Crawley Town 2-1 in the Sussex Senior Cup on Wednesday.
Albion went ahead at Villa Park when Aaron Connolly's shot was saved and Henrik Bjordal calmly fired home.
Brighton keeper Robert Sanchez made a terrific save and Villa had an effort ruled out for offside, before the Seagulls doubled their advantage midway through the second half.
Max Sanders crossed and Connolly glanced a header home from close range.
Albion first-team players were quick to praise the club's youngsters on Twitter. Glenn Murray wrote "Nice work lads" and Shane Duffy tweeted "Go on the lads congratulations fully deserved been superb all season."