Evan Ferguson scored twice in the first half as Brighton beat Southampton in the Premier League to secure European football for the first time in their history.
The 18-year-old forward opened the scoring with a powerful low shot past Saints goalkeeper Alex McCarthy before doubling the Seagulls' advantage with a first-time finish from inside the area.
Mohamed Elyounoussi's glancing header offered the visitors brief hope of a comeback but Pascal Gross fired in a third to seal victory for the hosts.
Brighton strengthened their grip on sixth place in the table and have all-but qualified for next season's Europa League because of their superior goal difference over seventh-placed Aston Villa.
A point from their two remaining matches will confirm a sixth-placed finish but victory over their south-coast rivals assures Brighton of a Europa Conference League spot at the very least.
Southampton, whose relegation was confirmed with their defeat by Fulham last time out, will finish their top-flight campaign against Liverpool at St Mary's next Sunday.
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'We're all going on a European tour'
The Brighton fans were in buoyant mood as the game kicked off in the sunshine at the Amex Stadium.
The Seagulls, one of the success stories of the campaign, were heading for Europe and their fans enjoyed every moment by taunting the visitors, who in contrast will be watching their side in the Championship next season.
On the pitch, the hosts were quickly into their stride and Kaoru Mitoma should have put them ahead when he drove into the area only to shoot wide from close range.
McCarthy nearly handed Brighton an easy second as the Japanese forward latched on to the keeper's loose pass but could only hit the post with his lifted attempt.
The deadlock was eventually broken when Alexis Mac Allister teed up Ferguson, who took a touch to set himself before smashing the ball through the legs of Lyanco and under McCarthy, who will be disappointed not to have kept it out.
Ferguson took his tally to 10 goals for the season 11 minutes later when the vibrant Mitoma shrugged off Romeo Lavia's challenge and picked out the Irishman, who found the corner of the net with a composed strike.
Southampton were boosted by Elyounoussi's header from a corner but Gross equalled Glenn Murray and Neal Maupay's Premier League club record of 26 goals with a fierce swipe of his left boot.
Brighton fans cheered the final whistle with renditions of "We're all going on a European tour" - something they can look forward to for the first time ever next season.
Struggling Saints turn attentions to fresh start.
Saints arrived at the Amex with their fate already sealed. In reality, their relegation has seemed inevitable for some time and defeat by Brighton was a 12th top-flight game without a win.
The visitors looked bereft of ideas and intensity but they could have taken the lead before the Seagulls took control when Carlos Alcaraz fired wide after a brisk counter-attack.
It meant Brighton could make their dominance count through Ferguson's double and Elyounoussi's goal just before the hour mark was Southampton's first attempt on target.
However, minutes later Theo Walcott thought he had beaten the offside trap to stun the hosts with an equaliser - with an initial burst of pace to run clear followed by the composed finish which has typified his career - but the goal was chalked off by the tightest of margins following a video assistant referee review.
Gross' goal killed Southampton's challenge and meant a fourth away game in a row in which they had conceded at least three goals, for the first time since 2012-13.
On a bright note for the visitors, right-back Tino Livramento made his return after 13 months out with an anterior cruciate ligament injury he sustained in the corresponding fixture last season.
Saints will want to end their stay in the Premier League on a high against Liverpool but work will already have begun behind the scenes as they prepare to launch a promotion bid at the first time of asking, with Swansea boss Russell Martin heavily linked to lead the charge.
Speaking about his future, current Saints boss Ruben Selles said he "expects respect" from the club.
"If the club want to make a a decision before the end of the season, I expect some respect and communication before or I will be very disappointed," said Selles.