Danny Ings struck his 20th Premier League goal of the season as Southampton fought back to secure a 1-1 draw which almost certainly guarantees safety for Brighton.
South coast rivals Albion, who moved six points clear of the relegation zone with only two fixtures remaining, led at St Mary’s courtesy of Neal Maupay’s first-half strike.
Tariq Lamptey’s throw-in from the right was flicked on by the unmarked Glenn Murray, allowing Frenchman Maupay time and space to drill home left-footed and claim his 10th goal of the season.
Maupay’s strike meant he became only the second Brighton player after 36-year-old Murray to reach double figures in a Premier League season.
Saints were far from their fluent best in a disappointing first half and were correctly denied a 39th-minute leveller.
Lamptey’s blushes were spared by an offside flag after he inadvertently turned the ball into his own net having seen Ings’ initial effort diverted onto the crossbar by keeper Ryan.
Ings was then unfortunate to curl against the right post from the edge of the box before substitute Adams’ follow-up attempt was superbly blocked on the line by Brighton captain Lewis Dunk.
Southampton’s pressure eventually paid off with 24 minutes to go.
Ings, who remains with an outside chance of claiming the Golden Boot, was sent scampering away by Nathan Redmond’s through ball and he calmly drew Ryan before slotting into the bottom right corner.
The Seagulls were then indebted to keeper Ryan when he somehow got fingertips to a thunderous 25-yard strike from Vestergaard to turn it on to the underside of the crossbar.
Albion dug in during six minutes of added time to make it six away games without defeat and, but for a remarkable goal difference swing, will be playing top-flight football for a fourth successive season.
Final score: Brighton and Hove Albion 1-1 Southampton