Middlesbrough gain promotion at Derby County's expense
Both sides began the game knowing that victory would see them join champions Burnley in the top flight next season, though a draw was enough for Boro to pip the Seagulls to second place on goal difference.
Cristhian Stuani's goal, from Gaston Ramirez's superb free-kick and David Nugent's touch across, put the hosts on their way in the first half.
Another free-kick led to Dale Stephens' equaliser, heading across goal at the back post after Brighton had begun the second period in full flow.
But Stephens was then dismissed for a foul on Ramirez - and Boro made the man advantage count to retain the scoreline for the rest of the game, including eight minutes of added time.
The decision by chairman Steve Gibson to invest in playing staff for head coach Aitor Karanka was justified as two of the imports he helped finance came to the fore in Stuani and Ramirez.
It was Gibson's intervention 30 years ago that scraped the club off the canvas with extinction looming and his name was sung lustily by supporters before and during the game.
He oversaw the 2004 League Cup win at Cardiff and the run to the Uefa Cup final two years later, but few afternoons at the Riverside will have been as significant as this one.
Premier League money, a minimum of £170m, will prove hugely beneficial to a club that have faced tough economic times in their transition to the Championship.