Didier Drogba and John Terry looked to have snatched victory from the jaws of defeat with goals in the final six minutes at Stamford Bridge but the hosts' poor defending cost them when Ciaran Clark nodded home a late equaliser.
Both sides had held the lead in an exciting game, with Frank Lampard's penalty cancelled out by Ashley Young's spot-kick and Emile Heskey's header giving Villa the lead.
What a finish: Ciaran Clark heads his stoppage time equaliser
The result left Chelsea marooned infifth place, six points behind Manchester United having played a gamemore, and crucially outside the Champions League places.
That will place manager CarloAncelotti's position under fresh scrutiny, while opposite number GerardHoullier may enjoy some respite after ending a run of six defeats inseven games.
Chelsea began the match buoyed fromending their worst set of results for 11 years in Wednesday's ugly 1-0win over Bolton. But for all their early possession, they once againlacked any real penetration.
Jeffrey Bruma - making his fullPremier League debut - saw a header from a corner blocked but thebetter chances all fell to Villa, with Gabriel Agbonlahor, Ashley Youngand Stewart Downing all going close.
It's going in: John Terry scores to put Chelsea 3-2 ahead
But a sudden loss of discipline costthem dear, captain Stiliyan Petrov booked for a stupid lunge on FlorentMalouda moments before James Collins climbed all over the Frenchman toconcede a penalty.
Malouda did throw himself to thefloor, and Brad Friedel and Collins were both cautioned for protesting,but it was a definite foul and Lampard stepped up to convert his firstgoal since August.
Villa's frustration got the betterof them and they were penalised for more than one late tackle, whileReo-Coker, Agbonlahor and Clark were all booked before half-time.
Clark and the recalled Richard Dunneboth missed glorious chances to level when they headed and hooked over,respectively, from close range as Chelsea's defence went to sleep.Dunne also produced a last-gasp tackle to stop Malouda and a vitalclearance to thwart Michael Essien.
Relief: Chelsea players and manager Carlo Ancelotti celebrate Didier Drogb'a late equaliser
Ramires was booked for clippingPetrov's heels and Villa's pressure finally told when Essien's clumsytackle on Reo-Coker handed them a penalty four minutes before thebreak. Young made no mistake from the spot.
Collins nodded another half-chancetoo close to Petr Cech before half-time and Villa picked up where theyhad left off right from the restart. AndHeskey put them ahead just two minutes in when he climbed above youngBruma to power home Downing's excellent right-wing cross.
The former England player was then booked for a late tackle on Essien as Chelsea began to wake up to their predicament. Lampard, Drogba and Ramires all saw shots blocked before the latter drilled just wide after the ball broke to him in the box.
Shock to the system: Aston Villa celebrate Emile Heskey's second-half strike at the Bridge
The weakness of Ancelotti's bench was summed up when he sent on Jose Bosingwa for Paulo Ferreira. Lampardwas unlucky not to level in the 63rd minute when he sent a viciousvolley straight at Friedel, who then brilliantly closed down Malouda asthe forward tried to slot Lampard's ball through the keeper's legs.
Ancelotti threw on Salomon Kalou for Ramires for the final 17 minutes. Downingdrilled straight at Cech from 25 yards before Terry was carded for alunge on Young and Ancelotti played his final card by introducingDaniel Sturridge for Nicolas Anelka.
Ear we go: Aston Villa's Ashley Young celebrates his equalising spot-kick
Chelsea were denied in the final 10minutes by some desperate Villa defending as the visiting fans began tochant 'You're getting sacked in the morning!' at Ancelotti.
But Drogba came to his manager's rescue six minutes from time with the ugliest of equalisers. The struggling striker's miscontrol set up Kalou, whose shot was blocked back for Drogba to rifle home via Carlos Cuellar.
Drogba then nodded over Malouda's corner after Villa had brought on Marc Albrighton for an injured Agbonlahor.
Flying start: Frank Lampard crashed home the penalty before celebrating with Didier Drogba
With barely a minute remaining, Chelsea snatched what they thought was a winner. Drogba'sbullet header was parried by Friedel straight to Terry, who produced asuperb sidefoot finish to spark wild celebrations, with Ancelottimobbed by his own players.
But the joy was short-lived, with Clark stealing in completely unmarked at the back post to nod in Albrighton's cross.
Rough and tumble: Aston Villa brought their physical game to Stamford Bridge
There was still time for Drogba tovolley Bosingwa's cross wide and Albrighton to mishit a volley as bothsides poured forward in search of a winner.
But Chelsea had to eventually settle for a point, and will need to improve their form considerably to get back into the title race in the coming months.
Yellow peril: Gabriel Agbonlahor was just one of a number of Villa players to be booked
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