The 31-year-old has established himself as a firm fans' favourite at St Mary's since joining from Bristol Rovers in August 2009 and has seen his stock rise considerably during his debut top-flight season.
Lambert was rewarded for his performances with a new deal until 2016 during the international break and repaid Southampton in spectacular fashion.
Making his 500th career league appearance, the Liverpudlian curled home a spectacular 25-yard free-kick to rack up his 14th league goal of the campaign - more than any other English player in the Premier League.
Saints had gone ahead through another in-form striker, Jay Rodriguez, who collected a neat one-two from Steven Davis before slotting home in the 23rd minute.
Fernando Torres had a goal disallowed and Victor Moses saw a cross-shot deflect behind off Luke Shaw before Chelsea snatched a 33rd-minute leveler.
Marko Marin sent in the resulting corner and kamikaze defending allowed captain John Terry to head home unmarked from six yards.
Chelsea were level for less than two minutes, though, thanks to a moment of magic from Lambert.
After Steven Davis was fouled by Ryan Bertrand, Lambert stepped up to fire home a thunderous 25-yard free-kick into Petr Cech's top-right hand corner.
Chelsea peppered the Southampton goal throughout the second half but were unable to find a way past substitute goalkeeper Kelvin Davis, leading to a defeat that drops Rafael Benitez's side to fourth.
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