The 31-year-old struck in injury time to register his 11th Premier League goal of the season and assure Mauricio Pochettino's men of an eighth-placed finish
The forward, who started the match on the bench, took advantage of Ashley Williams’ poor clearance to bundle the ball over the line and register his 11th Premier League goal of the season.
The result means Southampton are assured of an eighth-place finish at the end of the campaign.
|By Tom Maston
In what was a match that typified an end of season warm-down between two sides with little to play for, it was a comical moment which won it for Southampton.
Rickie Lambert will claim the injury-time goal and in truth it was the least Mauricio Pochettino’s side deserved after showing much more adventure.
Luke Shaw was outstanding on the left side while Nathaniel Clyne also put in a sterling performance on the opposite flank, and after securing their safety last week Swansea looked devoid of ideas as to how to stop them.
Going forward, Southampton in look far better shape to continue their development heading into next season. Whether they have the same make-up by August remains to be seen.
A lack of significant incentives for either side contributed to a low-key encounter at the Liberty Stadium, with clear-cut chances in scarce supply.
The hosts enjoyed the majority of possession, but failed to cause Swansea goalkeeper Michel Vorm too many problems, while Artur Boruc had a comfortable 90 minutes at the other end.
Wilfried Bony and Sam Gallagher each wasted opportunities to break the deadlock after both players sent efforts over the crossbar in the opening period.
Swansea squandered another chance as Jonjo Shelvey squared the ball to Bony, who back-heeled to Pablo Hernandez, but Boruc denied the Spaniard before Jonathan de Guzman blazed over.
Dejan Lovren curled a 20-yard free-kick narrowly over the crossbar in 20th minute, before a Gallagher header from a dangerous Nathaniel Clyne cross suffered the same fate just past the half-hour mark.
Bony should have put Swansea in front soon after, but after collecting the ball from a Hernandez touch, the Ivorian powered his effort well over.
Adam Lallana's 25-yard drive shortly after the break forced Vorm into his first real save of the encounter, while the biggest cheers from home supporters came as news of fierce rivals Cardiff City's slide towards relegation filtered through.
Goalscoring opportunities were at a premium for both sides, and Shelvey's low free-kick on the hour was too tame to trouble Boruc in the Southampton goal.
But Southampton had the final say, as Lambert put the ball in the back of the net to secure the club’s 15th win in the Premier League this term.