By Phil McNulty Chief football writer at Stamford Bridge
Robin van Persie's double sealed an amazing win for Arsenal
Arsenal's up and down season is in the ascendancy again after Robin van Persie struck twice in three second-half minutes to stun Premier League leaders Chelsea at Stamford Bridge.
Johan Djourou turned Jose Bosingwa's cross into his own net after 31 minutes to give Chelsea the lead as Arsenal's title challenge looked to be in danger of suffering a potentially fatal blow.
And then, with Chelsea the dominant force, Van Persie delivered two crucial blows to earn Arsene Wenger's side a priceless victory.
He looked well offside when he drilled home the equaliser after 59 minutes, then was on target again on the turn to complete a remarkable turnaround in fortunes.
Arsenal are turning into the Premier League's great enigmas, responding with victories against Manchester United and now Chelsea just when they were being written off as serious title contenders.
Chelsea, meanwhile, are suffering at the place that was once their greatest strength - Stamford Bridge.
Wenger praises Arsenal spirit
After four years of impregnability at home, Chelsea have now lost to Liverpool and Arsenal this season and have won only three out of eight league games at Stamford Bridge.
Arsenal knew they could not afford to slip up if they were to maintain a serious title challenge, and they started with real attacking intent.
Chelsea keeper Petr Cech was in action in the 13th minute, plunging to save from Samir Nasri's low shot, with William Gallas - taunted mercilessly by the home fans - just failing to apply a crucial touch from the rebound.
Cesc Fabregas then tested Cech again before Chelsea demonstrated their threat, with a slick exchange between Frank Lampard and Deco almost creating an opening for Nicolas Anelka.
Arsenal's early promise was then undermined when they conceded the sloppiest of goals just after the half hour.
Goalkeeper Manuel Almunia gifted Chelsea possession with a wayward throw, and when Bosingwa drove in a dangerous low cross from the right, Djourou could only slide the ball into his own goal at the near post.
In contrast to his strike partner Adebayor, Van Persie had been industrious and he tested Cech with a shot on the turn as Arsenal looked to fashion a quick response to Chelsea's goal.
Arsenal's carelessness at the back almost allowed Lampard to double Chelsea's advantage six minutes after the break, the England midfield man failing to make a proper connection with an opening on the edge of the box.
Wenger's side needed a lifeline from somewhere, and they were thrown one by the officials as they equalised in dubious circumstances just before the hour.
Scolari unhappy with officials after defeat
Van Persie looked well offside as he was found inside the area by Denilson's pass, and as Chelsea waited for a flag that never came the Dutch striker flashed an emphatic finish high past Cech.
And a remarkable turnaround was complete three minutes later when Van Persie struck against to put Arsenal in front.
Adebayor rose to head down Fabregas' free-kick, and Van Persie produced a stunning low finish to beat Cech again.
Chelsea, inevitably, pressed but Arsenal looked just as likely to add a third, with Cech saving well from Denilson deep in injury time.
Arsenal boss Wenger celebrated with his staff at the final whistle, an indication of just how important he feels this victory can be.
Chelsea's fans, in contrast, greeted the final whistle with jeers.
Chelsea: Cech, Bosingwa, Ivanovic, Terry, A Cole, Mikel (Malouda 69), Deco (Stoch 81), Ballack, Lampard, Kalou, Anelka.
Subs Not Used: Hilario, Bridge, Ferreira, Mineiro, Alex.
Booked: Terry, Ivanovic.
Goals: Djourou 31 og.
Arsenal: Almunia, Sagna, Gallas, Djourou, Clichy, Denilson, Fabregas, Song Billong, Nasri, Adebayor (Bendtner 83), Van Persie.
Subs Not Used: Fabianski, Vela, Ramsey, Silvestre, Wilshere, Gibbs.
Goals: Van Persie 59, 62.
Ref: Mike Dean (Wirral).
BBC Sport Player Rater man of the match: Arsenal's Robin Van Persie (8.01 on 90 minutes).
Please note that you can still give the players marks out of 10 on BBC Sport's Player Rater after the match has finished.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.