Gabriel Agbonlahor's equaliser ensured Aston Villa ended Chelsea's 100% home record this season and kept up their own unbeaten Premiership start.
Teenager Agbonlahor scored his third goal for Aston Villa
The hosts scored after less than three minutes when Didier Drogba bundled home his eighth goal of the season.
But 19-year-old Agbonlahor got a deserved equaliser for Villa just before half-time, nodding in Liam Ridgewell's astute header.
Salomon Kalou could have won it for Chelsea at the death but headed wide.
It was a frustrating afternoon for the champions, for whom Andriy Shevchenko is still without a goal since the second game of the season.
However, the Blues' increasingly desperate attempts to find a winner coupled with Villa's impressive performance made for a pulsating encounter at Stamford Bridge.
Martin O'Neill had promised his side would not be intimidated by the champions but keeper Thomas Sorensen looked to have forgotten that message when he was easily beaten to Arjen Robben's free-kick by John Terry.
The England captain nodded the ball down to Drogba's feet, who bundled home his 13th goal in 16 games.
The lead secured after just two minutes and 41 seconds, Chelsea continued to pressure the visitors.
Frank Lampard was denied by a magnificent save from Sorensen and suddenly, Villa's record of not having won away in the league since February seemed more telling than their unbeaten start to the season.
But O'Neill's assertion that they would have chances to score at Stamford Bridge proved spot on.
Stilian Petrov had a decent shot saved by Petr Cech and Juan Pablo Angel should have done better than blaze over from a corner.
As the clock hit 44 minutes, Chelsea, who had not conceded a goal in the first-half all season, might have been confident of taking a lead in at half-time.
However, their defence was caught out by some quick thinking, first from Steve Davis, who floated a perfect ball to an unmarked Ridgewell at the far post after a corner had been cleared.
Ridgewell unselfishly directed his header across goal where Agbonlahor nodded home.
The goal instilled new-found belief into Villa and they might have sneaked a lead before half-time when substitute Milan Baros skipped through Chelsea's shellshocked defence but scuffed his shot.
The pattern continued after the break, Agbonlahor frequently threatening the home defence with his electric pace.
Jose Mourinho responded with a double change and it nearly came off.
Shaun Wright-Phillips had already hit the bar when Kalou's shot was deflected to the England winger with the keeper stranded - but he could not get the shot on target.
And after Shevchenko had seen a wonderful curling shot saved by Sorensen, Kalou leapt for a header at the death but somehow planted it wide.
Chelsea boss Jose Mourinho:
"The result is not fair. One team tried to win, the other tried to get a draw.
"I think it was our best game of the season. We produced incredible football and I think 10 great chances.
"I wouldn't have been surprised if they had scored a winner at the end. It just wasn't our day."
Aston Villa boss Martin O'Neill:
"I enjoyed it. We got off to a very poor start and looked more than a bit apprehensive.
"But we got more positive and deserved to be level at half-time. We came under severe pressure in the second half, but we were a threat to them.
"There's a bit more confidence in the side now and on another day we could have caved in. We showed resilience."
Chelsea: Cech, Geremi (Kalou 68), Ricardo Carvalho, Terry, Ashley Cole, Essien, Makelele, Lampard, Shevchenko, Drogba, Robben (Wright-Phillips 68).
Subs Not Used: Cudicini, Boulahrouz, Obi.
Goals: Drogba 3.
Aston Villa: Sorensen, Hughes, Mellberg, Ridgewell, Barry, Davis (Laursen 83), McCann, Petrov, Agbonlahor, Angel, Moore (Baros 40).
Subs Not Used: Taylor, Whittingham, Berger.
Booked: McCann, Mellberg.
Goals: Agbonlahor 45.
Ref: G Poll (Hertfordshire).