Wayne Rooney and Javier Hernandez lead astounding comeback for Manchester United.
The home side was riding high on a three-goal lead shortly before the hour mark, with an own goal from Jonny Evans and a David Luiz header either side of a Juan Mata stunner giving the Blues the advantage.
But United unleashed a second half onslaught to rescue a point at the Bridge, with Rooney and Javier Hernandez the heroes for the Red Devils.
United went into the game having failed to win in its last nine visits to Stamford Bridge in the Premier League, and looked to the returning duo of Wayne Rooney and Ashley Young to spearhead the attack along with Danny Welbeck.
Chelsea, meanwhile, handed a first start to new signing Gary Cahill, with skipper John Terry ruled out through injury.
The game had the feel of a usual heavyweight bout in the opening 20 minutes, with each side attempting to feel its way in to the game without leaving itself exposed to the counterattack.
United had the lions’ share of possession in the opening exchanges, and looked the more likely to break the deadlock as Rooney and Welbeck began to combine well up top.
The visiting side was left to feel aggrieved with referee Howard Webb as the team had two strong penalty appeals turned down within the space of 10 minutes. First Young went over under a nudge from Jose Bosingwa, then Welbeck was felled by Cahill as he ran through on goal, but neither decision went the way of the Red Devils.
The game remained fairly balanced towards the end of the half, but then out of the blue, the Blues struck the first blow.
Mata and Fernando Torres worked the space to the left of United’s penalty area and Daniel Sturridge found his way in behind Patrice Evra before running at the near post. His cut back took a nick of David De Gea’s outstretched leg before striking Jonny Evans in the chest and nestling in the back of the net.
The goal brought the game to life, as Sturridge then tested De Gea from distance before a United onslaught closed out the first half, with Petr Cech denying Rooney on two occasions.
Sir Alex Ferguson’s side looked the most likely to grab the next goal, but just 40 seconds after the restart, Chelsea doubled the lead in emphatic style.
Torres got the ball in space on the right flank, and picked out Mata with a pin-point cross before the former Valencia man rifled home a sumptuous volley from inside the area.
And just five minutes later, Villas-Boas’ side had a third, after Mata’s free kick was flicked on by David Luiz and turned home by Rio Ferdinand’s shoulder.
It was further insult to the England international, as he suffered a torrent of abuse from the home fans throughout due to the on-going race row between his brother Anton and John Terry.
Desperate for a way back in to the game, Ferguson threw on Javier Hernandez to bolster the attack, and shortly before the hour mark, United grabbed a lifeline.
Sturridge brought down Evra inside the Chelsea box, and it was third time lucky for the visitors as referee Webb pointed to the spot. Rooney crashed home the ensuing penalty in to the top corner to keep his side in the game.
Despite chances for both sides, it was United which struck next, again from a Rooney penalty, after Welbeck was caught by the outstretched leg of Ivanovic following good work from Hernandez.
The Bridge had gone from rocking to rocky, and it almost got worse for the home side when substitute Oriol Romeu gave the ball away in his own half, but Hernandez could only fire wide across goal after being played in by Giggs.
Torres was then gifted a golden opportunity as a simple ball bounced over Evans’ head, but the Spaniard dallied on the it after driving goalwards and was eventually robbed by Valencia.
And with less than 10 minutes to go, Torres – and Chelsea – was left to rue that miss, as United's famous comeback was completed.
Valencia and Welbeck combined well down the right. The former’s cross was gathered in by Rooney, whose shot was parried by Cech to Giggs before the Welsh veteran picked out Hernandez with a cross. The Mexican made no mistake and headed home the equalizer.
Chelsea could have stolen the three points at the death when Mata's free kick seemed destined for the top corner, but De Gea did brilliantly to turn the ball behind.
In the end, the sides had to settle for a point apiece from a match which will rightly go down in the annals of Premier League classics.