A dramatic injury-time winner from James Beattie gave Saints their first win in six games after they had let slip a two goal lead.
Beattie, who had not previously scored in 18-months thundered home a 28-yard free-kick into the top right corner following a foul by Dennis Wise on Marian Pahars.
The big striker had previously ended his goal drought inside three minutes slotting home from close range from a cross by Wayne Bridge - his first senior goal since May of last year.
Jo Tessem bundled in the second from close range after 36-minutes against a flat Chelsea side who did not manage a first-half shot on target.
But the visitors stepped up the tempo after the break as Saints sat deep to hand them the initiative and they levelled with two goals in nine minutes, the first hooked home by Dennis Wise on 68-minutes and the second a free-header by Gustavo Poyet 13 minutes from time.
Saints were defending desperately looking to hang on for a point against a Chelsea side who have not won away since April. But Southampton's hopes of victory looked to have gone when Jo Tessem had a diving header kicked off the line two minutes from time but then Beattie crashed in the injury-time winner to lift his side out of the relegation zone with their first victim since September 23.
* For full match reports and picture's see tonight's Pink and Monday's Southern Daily Echo.
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