Fabian Delph's third Barclays Premier League goal gave Villa a magnificent victory over high-riding Chelsea, bringing to an end the Londoners' 14-match unbeaten league run.
And in an explosive finish, the visitors had Ramires sent off for a crude tackle on Karim El Ahmadi, while manager Jose Mourinho was ordered from the touchline for disputing the decision.
The dismissal of Ramries meant the visitors finished the match with nine men, Willian having been sent off in the 69th minute after being booked for the second time.
But the visitors' lack of numbers shouldn't detract from a fabulous victory clinched by Delph's 84th-minute winner.
The goal wasn't as spectacular as his previous efforts against Southampton and Albion, but it was every bit as vital.
It was certainly a day to forget for the outspoken Mourinho.
His side hadn't lost a league match since early December but he has still never managed a win at Villa Park.
After a cagey opening 10 minutes notably only for an injury to Willian and a booking for Nathan Baker's foul on Fernando Torres, the game suddenly came to life with a chance at either end in the space of 60 seconds.
Willian's deflected shot was comfortably saved by Brad Guzan before good approach work by Gabby Agbonlahor and Ashley Westwood set up Delph for a left-wing cross which was headed wide by Christian Benteke at the far post.
That was quickly followed by another Willian shot which flashed narrowly off target, Villa responding with a 25-yarder which flew too high following Benteke's astute pass.
As the teams continued to trade blows, Oscar sent a low angled drive narrowly beyond the far upright before former Villa defender Gary Cahill got in the way of Agbonlahor's snap shot from the edge of the area.
The orderly sequence of goal attempts was broken in the 29th minute, Nemanja Matic feeling the full force of Bacuna's piledriver after El Ahmadi's fine pass had created an opening for the Dutch right-back.
But Joe Bennett, enjoying a fine game at left-back, had to be alert five minutes later, heading away a dangerous Ramires centre as Torres lurked menacingly just behind him.
For all that, Villa were matching the leaders and in the 39th minute they were within inches of going ahead.
Agbonlahor headed on for Benteke, whose spectacular volley from the edge of the area flashed narrowly wide of the left-hand post.
There was huge relief a couple of minutes later, though, Matic forcing the ball home at the far post following a Willian corner but handling in the process.
Chelsea stepped up the pace at the start of the second half and there was another let-off for Villa in the 49th minute when Branislav Ivanovic's deep cross was cut back from beyond the far post by Eden Hazard.
El Ahmadi was quickest to react but succeeded only in knocking the ball towards his own goal, forcing Guzan to make a one-handed save.
That was the prelude to a dominant spell by the visitors, although we were past the hour mark before Guzan was called into action again, the keeper holding a low shot from Oscar.
If Villa's attacks had become less frequent, though, they were close again on 66 minutes.
In a classic counter attack, Agbonlahor and Benteke combined superbly before Andi Weimann cut the ball back for the Belgium international to send a powerful low drive only marginally wide of the far post.
Villa's cause was given a further boost when Willian was sent off for his second bookable offence when he brought down Delph, and as they began to exert more pressure Bacuna's shot deflected for a corner off Cesar Azpilicuta, and Delph created space for a 20-yard shot which wasn't far off target.
And eight minutes from time, after Ron Vlaar had headed just over from Ashley Westwood's corner, the home side broke the deadlock.
Delph made a mazy run from the half-way line before slipping the ball wide to sub Marc Albrighton, who had ventured down the left.
The winger cleverly knocked the ball back inside, and Delph scooped his shot beyond keeper Petr Cech and into the far corner.
Benteke was close in the final minute, his fierce drive being palmed away by Cech, while Delph's low shot in stoppage time hit Cech's legs and landed on top of the bar before Ramires was sent off and Mourinho was ordered from the touchline.
Villa: Guzan; Bacuna, Vlaar, Baker, Bennett (Clark 78); El Ahmadi, Westwood, Delph; Weimann, Benteke, Agbonlahor (Albrighton 74). Unused subs: Steer, Albrighton, Sylla, Holt, Lowton, Robinson.
Chelsea: Cech; Ivanovic, Cahill, Terry, Azpilicuta; Ramires, Matic; Willian, Torres, Hazard, Oscar (Schurrle 67); Torres (Ba 67). Unused subs: Schwarzer, Lampard, Mikel, Salah, Kalas.