Georginio Rutter scored his fifth goal in the Premier League this season
Brighton scorched to an easy win at relegation-threatened Southampton thanks to goals from Joao Pedro, Georginio Rutter, Kaoru Mitoma and Jack Hinshelwood.
The Seagulls dominated from the outset, with Pedro's delicate chip over Aaron Ramsdale setting them on their way midway through the first half.
Saints rallied before the break, but the game was beyond the bottom-of-the-table hosts once Rutter finished from close range after 56 minutes.
Japan international Mitoma scored his fifth goal in seven games before defender Hinshelwood put the finishing touch on Southampton's 21st Premier League defeat of the season.
The margin of defeat would have been even wider for Southampton had Ramsdale not denied Carlos Baleba and Yankuba Minteh with some last-ditch saves in the closing minutes as Saints threatened to fall apart completely.
Southampton, led by Ivan Juric since late December, have won just twice in the league all season and look doomed with only 12 rounds of games remaining.
They are eight points adrift of Leicester City, who sit one place ahead of them in the relegation zone, and 13 points behind Wolves in the last safe position.
Brighton's Fabian Hurzeler, in his first season in charge, will be targeting a renewed push for a place in Europe with his side sitting eighth on 40 points.
Seagulls soar again
Hurzeler's side are unlikely to have such an easy ride as this in their remaining matches. They could have been out of sight by half-time against last season's Championship play-off winners.
Rutter's shot on the turn early on was blocked by Ramsdale's feet, and Mitoma should have scored when he stabbed a shot wide from inside the six-yard box.
Pedro, in for the injured Daniel Welbeck, combined well with Rutter to grab his sixth goal of the season before Brighton took their foot of the gas a touch ahead of half-time.
Southampton striker Cameron Archer's disallowed goal early in the second half, ruled out for offside, stung the Seagulls back into action as Rutter and then Mitoma ruthlessly capitalised on slack defending.
Japan international Mitoma is in a fine run of form for a Brighton side who have recovered from a sticky December, while 19-year-old Hinshelwood was mobbed by team-mates after drilling home his second goal of the season.
Three weeks have passed since Brighton lost 7-0 at Nottingham Forest, and three wins have followed.
With their next three games against Bournemouth, Newcastle and Fulham, a tilt at a second European campaign may not be beyond them.
Frail Saints look doomed
It is hard to see any way that Southampton can clamber to safety on the evidence of this display, despite having 36 points to play for.
Lesley Ugochukwu's booking for a reckless challenge on Pedro just under two minutes into the game set the tone, and Southampton captain Jan Bednarek did not make it beyond 12 minutes when he was forced off with an injury.
The home side did not have any touches of the ball in Brighton's penalty area in the first half, and only managed five after the break.
Kamaldeen Sulemana's shot after 69 minutes was their only attempt on target in the match, and the way Rutter and Mitoma sliced through the defence to extend Brighton's lead epitomised the woes at St Mary's.
They have conceded three or more goals in home Premier League games on nine occasions this season, and visits to Chelsea and Liverpool loom in their next two outings.
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