Match ends, Southampton 3, Liverpool 2.
Liverpool's hopes of a top-four spot were dented as Southampton dramatically snatched victory at St Mary's.
Liverpool had looked in command after Philippe Coutinho and Daniel Sturridge scored in a five-minute period.
Sadio Mane missed a penalty just after the break following Martin Skrtel's foul on Graziano Pelle, but made amends soon after with a smart finish.
Pelle's curling shot restored parity in the 83rd minute, before Mane pounced to seize all three points for his side.
Liverpool pressed forward to try to force a final twist, but a speculative penalty shout for a push on Christian Benteke was all they could muster.
Southampton remain seventh, with Liverpool two places lower and still seven points off the top four.
Reds' first half...
As the Reds departed the south coast, manager Jurgen Klopp was left to try to comprehend how they had contrived to lose from 2-0 up at half-time for the first time in the Premier League.
After Shane Long was denied an early penalty in a tussle with Dejan Lovren, the Reds took control of the first half with Coutinho's low curling effort followed in short order by Sturridge's cleverly-crafted second.
As Southampton searched for an immediate response, Liverpool exploited the space left behind with Joe Allen shooting into the shins of Fraser Forster from eight yards before seeing a goal chalked off for offside.
However, whether it was Thursday's Europa League exploits or the 10 games more they have played than Saints this season, Liverpool's slick passing and swift movement dried up markedly after the break.
When Mane's penalty - awarded after Skrtel's tug on Pelle - was pushed aside by goalkeeper Simon Mignolet early in the second half, it seemed that it was set to be the visitors' day.
But Ronald Koeman's introduction of Mane and Victor Wanyama at half-time throttled the supply to Liverpool's front men while adding a more clinical edge to his own attack.
After the electric Mane had escaped Mamadou Sakho to cut the deficit, the hosts kept believing as Liverpool kept retreating and the pressure finally told late on.
Sturridge - who played 68 minutes as his side completed a 3-1 aggregate Europa League win over Manchester United in midweek - had already been withdrawn wincing by that point, with full match fitness still some way away.
Man of the match - Sadio Mane
What they said
Southampton manager Ronald Koeman: "I was so happy for the players. It was a must-win game, the same as last week. We are still fighting for a European place, that is what we want.
"I'm proud of the team. We had a great spirit after half time and it was hard to manage it after 45 minutes."
Liverpool manager Jurgen Klopp: "The first half we played brilliant football, we have to close the game out. You have to accept in the second half they controlled the game.
"They scored three goals, we didn't, that is how football is."
Stats you need to know
- Liverpool lost a game in which they were leading by two or more goals at half-time for the first time in Premier League history, having previously won 112 and drawn three of 115 games.
- There were just two minutes and 24 seconds between Southampton's second and third goals.
- Southampton have lost just one of their past seven Premier League games at St Mary's , winning five, drawing one and losing one.
- Philippe Coutinho has scored more goals in all competitions for Liverpool in 2015-16 than in any other previous campaign with nine.
- Simon Mignolet has saved three of the last five penalties that he has faced in the Premier League for Liverpool, after saving one of the previous five.
- Graziano Pelle has scored in consecutive Premier League games for the first time since September 2014. Pelle also provided two assists in a Premier League game for just the second time in his career.
The international break means a pause to the Premier League action. Southampton travel to leaders Leicester on Sunday 3 April after it gets back under way, with Liverpool entertaining second-placed Tottenham the day before.
- 6José Fonte
- 17van Dijk
- 14RomeuSubstituted forWard-Prowseat 69'minutes
- 4ClasieSubstituted forWanyamaat 45'minutes
- 11TadicSubstituted forManéat 45'minutesBooked at 86mins
- 2Cédric Soares
- 6LovrenBooked at 25minsSubstituted forSkrtelat 45'minutesBooked at 49mins
- 23CanBooked at 48mins
- 24AllenSubstituted forOjoat 87'minutes
- 15SturridgeSubstituted forBentekeat 70'minutes
- 4K Touré
- 44B Smith
- Roger East
- Shots on Target
Second Half ends, Southampton 3, Liverpool 2.
Attempt missed. Philippe Coutinho (Liverpool) right footed shot from outside the box is too high.
Foul by Sadio Mané (Southampton).
Adam Lallana (Liverpool) wins a free kick on the left wing.
Attempt saved. Graziano Pellè (Southampton) right footed shot from outside the box is saved in the top right corner. Assisted by Sadio Mané.
Substitution, Liverpool. Sheyi Ojo replaces Joe Allen.
Sadio Mané (Southampton) is shown the yellow card for excessive celebration.
Goal! Southampton 3, Liverpool 2. Sadio Mané (Southampton) left footed shot from the centre of the box to the bottom right corner. Assisted by Graziano Pellè.
Goal! Southampton 2, Liverpool 2. Graziano Pellè (Southampton) left footed shot from outside the box to the bottom left corner. Assisted by Shane Long.
Victor Wanyama (Southampton) wins a free kick in the defensive half.
Foul by Joe Allen (Liverpool).
Attempt blocked. Joe Allen (Liverpool) right footed shot from outside the box is blocked. Assisted by Adam Lallana.
Foul by Cuco Martina (Southampton).
Philippe Coutinho (Liverpool) wins a free kick in the attacking half.
Foul by James Ward-Prowse (Southampton).
Emre Can (Liverpool) wins a free kick in the defensive half.
Foul by James Ward-Prowse (Southampton).
Joe Allen (Liverpool) wins a free kick in the attacking half.
Foul by Graziano Pellè (Southampton).