Crystal Palace put in their performance of the season to stun league leaders Chelsea as John Terry's own goal was enough to clinch a massive three points to help pull the Eagles away from the drop-zone.
Despite receiving the stroke of luck they had been missing over recent weeks, Tony Pulis' side were well worth their victory and had a number of chances to improve the lead, but were also indebted to Julian Speroni who made two superb stops to clinch victory in a pulsating encounter.
A quiet opening burst into life on 18 minutes when overlap from Cesar Azpilicueta allowed Eden Hazard to slip the ball into his path, and he flashed a low centre across the face of the Eagles' goal for Andre Schurrle who, under pressure from Joel Ward, could only stab the chance wide.
But soon after Yannick Bolasie found himself in the thick of the action with two opportunities falling his way in quick succession. Firstly he cut inside from the left, forcing Branislav Ivanovic to backpeddle and that allowed him a sight of goal but dragged his effort well wide.
Then two minutes later a nice move involving Jason Puncheon and Adrian Mariappa allowed the full-back to deliver a cross to the back post for Bolasie, but he attempted to control the ball before hitting it goalwards which forced him wider and meant he could only find the side-netting.
Jose Mourinho's side then escaped a couple of penalty appeals as Cameron Jerome and Bolasie went down under challenges from Gary Cahill, and Mile Jedinak hit a tame free-kick straight at Petr Cech as Palace enjoyed a decent spell of pressure.
It continued right up until half-time when Puncheon saw a first-time snap-shot fly over the bar when Cahill attempted to clear a Mariappa cross, and after enjoying the better of the opening 45 minutes their pressure finally told as they took the lead seven minutes into the second half.
Ward found himself himself with the ball on the left and lofted in a ball towards the near post where Joe Ledley was attacking, but it was Terry who met it first and inadvertently flicked the ball over Cech and into his own net to send Selhurst Park potty.
But minutes later the lead was only maintained thanks to the brilliance of Julian Speroni. Looking to inject the spark his Chelsea side needed, Hazard ghosted in from the left flank and curled a low shot towards the bottom corner, and despite seeing the ball through a crowd of bodies the Eagles keeper somehow managed to get down low and edge it past the post.
Bolasie and Ivanovic then both failed to hit the target with speculative attempts from range before the hosts were a whisker away from doubling their lead. Jerome bulldozed through the Chelsea defence and played in Puncheon who had bust a gut to get forward, and his shot beat Cech but trickled agonisingly wide of the post.
Terry nearly made amends when he met a corner but headed over, before Speroni again produced heroics to keep his side ahead when Oscar's scuffed shot fell perfectly for Hazard who looked destined to score, but the Argentine managed to make a diving save to push the ball away.
But Palace kept breaking on the counter and went even closer to sealing the win when Jerome found himself one-on-one with Cech, but after firing past the Czech keeper he rattled the base of the post. Moments later Ledley saw a volley flash wide of the mark and Puncheon drove straight at Cech as the Eagles looked to extend their fragile lead.
It was all Palace during this period and substitute Stuart O'Keefe forced Cech to tip the ball over with a blast similar to his goal against Sunderland back in August, but a loose pass by him allowed Torres a chance but he lofted the ball over the top.
But despite the league leaders pushing hard to save their title hopes, the Eagles stayed strong and kept the clean sheet in tact to record a first Premier League victory over the Blues and complete an afternoon no-one in Selhurst will ever forget.
Palace: Speroni, Mariappa, Dann, Delaney, Ward, Dikgacoi, Jedinak, Puncheon (Parr 90), Ledley, Bolasie (O'Keefe 70), Jerome (Murray 88).
Subs not used: Hennessey, McCarthy, Bannan, Ince.
Chelsea: Cech, Ivanovic, Cahill, Terry, Azpilicueta, Luiz (Oscar 46), Matic, Lampard (Salah 52), Schurrle (Ba 70), Hazard, Torres.
Subs not used: Hilario, Kalas, Mikel, Willian.