Goals from Morgan Schneiderlin, Rickie Lambert and Jay Rodriguez won the game and moved Southampton above Sunderland in the Premier League table, three points nearer to safety.
An entertaining match sparked into life from the start, the players perhaps having been jolted into a state of high alert by the bang of a red, pre-match smoke bomb set off by Liverpool fans protesting about season ticket prices. After lively opening exchanges, Southampton took the lead after six minutes, Rodriguez getting on the end of a floated Gastón Ramírez cross to the far post and knocking the ball down for Schneiderlin to flick home from five yards out after outmuscling Daniel Agger.
With Liverpool rattled and their defence in disarray, Southampton squandered excellent chances to increase their lead, Adam Lallana sending one surface-to-air screamer fizzing inches over the crossbar from distance, just before Lambert fluffed a one-on-one with Brad Jones after springing the offside trap with an impeccably timed run. Jones was forced into action again in the 22nd minute, saving well from Ramírez at his near post, but parrying the ball to Rodriguez, whose acrobatic follow-up went wide. Seconds later, the unmarked Rodriguez volleyed over from the same position.
The home side were rampant and it was a matter of when, not if, they would trouble the scoreboard operator for a second time. Lambert duly obliged with a free-kick from the inside left, his curling drive finding a gap in Liverpool's porous wall and deflecting past Jones off the backside that Daniel Sturridge had obligingly turned its way. By half-time, Southampton could and should have been six or seven up, with Rodriguez notching a hat-trick of near misses and Lallana also going close.
Having looked largely toothless and clueless, Liverpool gratefully snatched a lifeline in first-half injury time when Philippe Coutinho, a former charge of Southampton manager Mauricio Pochettino at Espanyol, drove home from six yards out after Sturridge's effort at redemption had been blocked. Before that point, a curiously out-of-sorts Liverpool had offered little, keeping Artur Boruc on his toes with harmless long-range efforts and pass-and-move forays that regularly broke down without any need for Saintly intercession.
Looking over their shoulders from a perch well within reach of the chasing posse, Southampton went into this match having ended a run of back-to-back defeats with last weekend's stalemate at Norwich. Nathaniel Clyne returned at right-back, with Maya Yoshida resuming his usual duties in the centre of defence and José Fonte dropping to the bench, only to return to action just after the half-hour mark after Jos Hooiveld limped off injured.
A nagging calf injury scuppered Pepe Reina's chances of passing a fitness test, hence Jones's presence between the sticks for the Merseyside team. In defence, Agger had returned in place of the injured Jamie Carragher, while central midfielder Joe Allen soldiered on despite fears his season had been prematurely ended by a shoulder injury that requires surgery. His match at St Mary's certainly ended prematurely, when the Liverpool manager, Brendan Rodgers, withdrew the Welshman at half-time and sent on Lucas Leiva.
Liverpool's performance improved after the break but their relegation-threatened hosts continued to look more composed and dangerous despite the partial erosion of their two-goal cushion. Steven Gerrard and Luis Suárez brought a few smart saves out of Boruc, and Sturridge shot wide, but Southampton's pace on the counter and relentless crossing from either flank continued to wreak occasional havoc among a visibly jittery Liverpool back four.
The same back four went awol when Rodriguez picked up the ball on the halfway line and ran at them with 10 minutes to go, allowing the midfielder to sprint undisturbed and fire a low drive past the hideously under-protected Jones.