The Seagulls can, mathematically, still be caught by third-placed Huddersfield who sit 15 points behind them ahead of their game with Derby later this evening.
But a 32 goal difference between the two all but guarantees Chris Hughton's men will be playing top flight football next season for the first time in 34 years.
Goals from Glenn Murray and Solly March looked to have the home side on course for a comfortable win but Ryan Colclough's late strike had nerves jangling at the Amex.
But they needn't have worried and stormed the pitch in their droves at full-time to celebrate.
Another win, at Norwich on Friday, will secure the tilte after econd-placed Newcastle United slumped to a 3-1 loss to Ipswich.
Elsewhere, third-placed Reading kept up the pressure on the Magpies and are now six points behind them after coming from a goal down to beat bottom side Rotherham 2-1 thanks to second-half strikes from Lewis Grabban and John Swift.
Fulham defeated Aston Villa 3-1, taking advantage of Leeds United's 1-0 loss to Wolverhampton Wanderers to climb above them into sixth position and the final playoff spot.
Sheffield Wednesday maintained their playoff push and are in fifth place on 75 points, two ahead of Fulham, after a 2-1 win at Queens Park Rangers.
Brighton: Stockdale, Saltor, Hunemeier, Dunk, Bong, Knockaert, Stephens, Kayal, March, Murray, Hemed.
Subs: Maenpaa, Skalak, Murphy, Norwood, Rosenior, Tomori, Akpom.
Wigan: Haugaard, Hanson, Buxton, Burn, Warnock, Power, MacDonald, Jacobs, Perkins, Tunnicliffe, Obertan.
Subs: Morsy, Connolly, Morgan, Powell, Colclough, Byrne, Gilks.
Referee: James Linington (Isle of Wight)