Nottingham Forest's Garath McCleary struck four times as Leeds conceded seven goals at home for the first time.
Robert Snodgrass put Leeds ahead with an early penalty but Forest hit back with goals from Adlene Guedioura, McCleary and Dexter Blackstock.
Luciano Becchio and Michael Brown pulled Leeds level only for McCleary to strike three times in the space of 15 minutes to stun the home side.
Blackstock struck his side's seventh to help Forest's battle against the drop.
“I'm quite embarrassed about the result”
Neil WarnockLeeds United boss
Forest manager Steve Cotterill labelled his side's win an "unbelievable game" as they astonishingly scored seven times against a Leeds defence who had conceded just a miserly two in five games since Neil Warnock took charge.
But there was little sign of things to come when Ross McCormack was brought down by Guedioura and Snodgrass scored from the spot to put Leeds ahead after just six minutes.
The home side barely had time to celebrate before on-loan midfielder Guedioura atoned for his mistake by producing a stunning 35-yard strike to equalise.
Winger McCleary, who went into the match with nine goals in 117 games, had proved a constant threat to Leeds and put the visitors ahead as he finished off a Forest counter-attack with a right-foot shot just before the break.
Leeds were booed off at half-time and they did little to appease their fans when Blackstock headed in an Andy Reid cross to extend Forest's lead.
GARATH McCLEARY IN FOCUS
Joined Forest from Bromley after a trial spell
He was mainly a substitute last season, making just eight league and cup starts
The winger offered a sign of things to come when he scored against Leeds last season at Elland Road
He had hit just nine goals in 117 games before Tuesday night's trip to Leeds
Becchio slotted in and Brown produced a half-volley to level for Leeds with two goals in as many minutes but the home side soon let their good work go to waste.
The Leeds defence was proving vulnerable and McCleary took advantage with three goals in quick succession.
He latched on to a Blackstock flick to drill in a shot, slotted in an effort after being set up by Reid and produced a measured finish to take his tally to four for the game.
Forest had been on the end of 4-0 and 4-1 drubbings from Leeds in the two prior fixtures but they gained retribution in emphatic manner when Blackstock scored a seventh.
Despite the defeat, Leeds remain five points from the play-off zone, while Forest are seven points above the relegation zone.
Leeds United manager Neil Warnock:
"I'm quite embarrassed about the result.
"But I don't think you learn much about your players when you're winning games, I think you learn things when things go against you, who stands up and who you want in the trenches with you.
"I've learnt probably more than I have in the other games, but in fairness some of them were just shattered."
Nottingham Forest boss Steve Cotterill:
"Garath McCleary comes from non-league. He's a special talent, he's raw, he's got two good feet, he can head it, he's strong. I think he can go on to be even better, I think he's a top lad.
"It was a stunning game, I know we've won but Leeds United played their part as well. Our chances went in, but they played their part.
"I thought it was an outstanding game by both teams. We're very pleased with the three points more than anything else, but to play in the manner we've played, we've done that a lot this season and ended up losing 1-0 so maybe it's evened out a little bit."
Full Time The game is over, as the referee blows his whistle.
Ross McCormack fouled by Chris Gunter, the ref awards a free kick. Ross McCormack restarts play with the free kick.
Effort on goal by Ross McCormack from inside the penalty area goes harmlessly over the bar.
A cross is delivered by Paul Connolly, Joel Lynch makes a clearance.
Luke Chambers challenges Billy Paynter unfairly and gives away a free kick. Ross McCormack takes the free kick.
The ball is swung over by Adam Clayton, Luke Chambers makes a clearance.
Foul by Adlene Guedioura on Ross McCormack, free kick awarded. Ross McCormack takes the free kick.
Unfair challenge on Greg Cunningham by Robert Snodgrass results in a free kick. Free kick taken by Lee Camp.
Lee Camp restarts play with the free kick.
Substitution Lewis McGugan is brought on as a substitute for Guy Moussi.
The offside flag is raised against Billy Paynter.
Substitution Ishmael Miller on for Dexter Blackstock.
Substitution (Nottm Forest) makes a substitution, with Scott Wootton coming on for Radoslaw Majewski.
Foul by Billy Paynter on Adlene Guedioura, free kick awarded. Free kick taken by Luke Chambers. The assistant referee signals for offside against Robert Snodgrass. Lee Camp takes the free kick.
Assist on the goal came from Garath McCleary.
80:43 Goal scored
Goal! - Dexter Blackstock - Leeds 3 - 7 Nott'm For Dexter Blackstock scores a goal from the edge of the penalty box to the bottom right corner of the goal. Leeds 3-7 Nottm Forest.
Substitution (Leeds) makes a substitution, with Billy Paynter coming on for Luciano Becchio.
Adam Clayton gives away a free kick for an unfair challenge on Andy Reid. Direct free kick taken by Andy Reid. Andy Reid takes a shot. Blocked by Luciano Becchio.
Ross McCormack takes a corner.
Corner taken by Ross McCormack from the left by-line, Header from close in by Luciano Becchio misses to the left of the goal.
70:54 Goal scored
Goal! - Garath McCleary - Leeds 3 - 6 Nott'm For Garath McCleary finds the net with a goal from inside the penalty area to the bottom left corner of the goal. Leeds 3-6 Nottm Forest.
The free kick is swung in left-footed by Robert Snodgrass, clearance made by Luke Chambers. Shot from 18 yards by Robert Snodgrass. Save by Lee Camp. Ross McCormack takes the inswinging corner, Danny Webber produces a header from inside the area that goes over the crossbar.
Booking Andy Reid receives a yellow card for unsporting behaviour.
Free kick awarded for a foul by Andy Reid on Robert Snodgrass.
Direct free kick taken by Ross McCormack.
Substitution Danny Pugh comes on in place of Paul Robinson.
Greg Cunningham concedes a free kick for a foul on Robert Snodgrass.
Guy Moussi has an effort at goal from outside the box which goes wide right of the goal.
Free kick awarded for a foul by Adam Clayton on Adlene Guedioura. Free kick taken by Luke Chambers.
Garath McCleary produces a drilled right-footed shot from 30 yards. Andy Lonergan makes a comfortable save.
Inswinging corner taken by Robert Snodgrass from the right by-line, Andy Reid makes a clearance.
Ross McCormack sends in a cross, clearance made by Joel Lynch.
Assist on the goal came from Andy Reid.
59:04 Goal scored
Goal! - Garath McCleary - Leeds 3 - 5 Nott'm For Garath McCleary finds the net with a goal from inside the penalty box low into the middle of the goal. Leeds 3-5 Nottm Forest.
A cross is delivered by Andy Reid,
Chris Gunter produces a cross.
Assist on the goal came from Dexter Blackstock.
55:46 Goal scored
Goal! - Garath McCleary - Leeds 3 - 4 Nott'm For Garath McCleary finds the back of the net with a goal from inside the penalty box to the top right corner of the goal. Leeds 3-4 Nottm Forest.
54:20 Goal scored
Goal! - Michael Brown - Leeds 3 - 3 Nott'm For Michael Brown finds the net with a goal from just outside the penalty box to the bottom right corner of the goal. Leeds 3-3 Nottm Forest.
The assist for the goal came from Robert Snodgrass.
52:50 Goal scored
Goal! - Luciano Becchio - Leeds 2 - 3 Nott'm For A goal is scored by Luciano Becchio from close in to the bottom left corner of the goal. Leeds 2-3 Nottm Forest.
Andy Reid provided the assist for the goal.
51:14 Goal scored
Goal! - Dexter Blackstock - Leeds 1 - 3 Nott'm For Dexter Blackstock grabs a headed goal from close in. Leeds 1-3 Nottm Forest.
Corner crossed in by Andy Reid. Outswinging corner taken by Andy Reid from the left by-line. Andy Reid crosses the ball,
Corner taken by Andy Reid, Paul Connolly makes a clearance. Adam Clayton fouled by Andy Reid, the ref awards a free kick. Andy Lonergan takes the free kick.
The second half begins.
Substitution Danny Webber replaces Aidan White.
45:00 +3:14 Half time
Half Time The referee calls an end to the first half.
Luciano Becchio produces a left-footed shot from outside the penalty area and misses left.
Assist by Adlene Guedioura.
45:00 +1:08 Goal scored
Goal! - Garath McCleary - Leeds 1 - 2 Nott'm For Garath McCleary gets on the score sheet with a goal from deep inside the penalty box to the top left corner of the goal. Leeds 1-2 Nottm Forest.
Aidan White takes a shot. Joel Lynch gets a block in. Inswinging corner taken left-footed by Robert Snodgrass from the right by-line, Guy Moussi makes a clearance.
Inswinging corner taken left-footed by Robert Snodgrass from the right by-line, Lee Camp makes a save. Inswinging corner taken from the left by-line by Ross McCormack, Guy Moussi manages to make a clearance.
Pass corner from right by-line crossed in by Andy Reid, save made by Andy Lonergan. Effort on goal by Garath McCleary from just outside the area goes harmlessly over the target.
The ball is sent over by Greg Cunningham.
Foul by Aidan White on Adlene Guedioura, free kick awarded. Andy Reid crosses the ball in from the free kick.
Garath McCleary produces a right-footed shot from just outside the box that misses to the right of the net.
Andy Reid has an effort at goal. Paul Connolly gets a block in. Short corner taken by Andy Reid. The ball is crossed by Andy Reid, Paul Connolly manages to make a clearance.
Garath McCleary sends in a cross, save by Andy Lonergan.
Corner from the left by-line taken by Andy Reid, Tom Lees makes a clearance.
Luciano Becchio gives away a free kick for an unfair challenge on Adlene Guedioura. Direct free kick taken by Luke Chambers.
Guy Moussi challenges Ross McCormack unfairly and gives away a free kick. Free kick crossed by Robert Snodgrass.
Direct free kick taken by Chris Gunter. The ball is delivered by Andy Reid, Tom Lees manages to make a clearance.
Booking Booking for Paul Robinson for unsporting behaviour.
Paul Robinson concedes a free kick for a foul on Dexter Blackstock.
Aidan White gives away a free kick for an unfair challenge on Chris Gunter. Free kick taken by Chris Gunter.
Andy Reid takes a shot. Save by Andy Lonergan.
Foul by Robert Snodgrass on Chris Gunter, free kick awarded. Lee Camp restarts play with the free kick.
Robert Snodgrass concedes a free kick for a foul on Chris Gunter. Direct free kick taken by Chris Gunter.
The ball is delivered by Garath McCleary, clearance by Paul Connolly.
Free kick awarded for an unfair challenge on Garath McCleary by Robert Snodgrass. Andy Reid crosses the ball in from the free kick, Andy Lonergan makes a comfortable save.
Unfair challenge on Radoslaw Majewski by Darren O'Dea results in a free kick. Greg Cunningham restarts play with the free kick.
7:11 Goal scored
Goal! - Adlene Guedioura - Leeds 1 - 1 Nott'm For Adlene Guedioura scores a brilliant goal from 35 yards. Leeds 1-1 Nottm Forest.
The assist for the goal came from Ross McCormack.
5:32 Goal scored
Goal! - Robert Snodgrass - Leeds 1 - 0 Nott'm For Placed penalty scored by Robert Snodgrass. Leeds 1-0 Nottm Forest.
Adlene Guedioura gives away a Penalty for an unfair challenge on Ross McCormack.
Free kick awarded for a foul by Joel Lynch on Luciano Becchio. Free kick taken by Paul Robinson.
Unfair challenge on Dexter Blackstock by Darren O'Dea results in a free kick. Lee Camp takes the direct free kick.
A cross is delivered by Chris Gunter, Dexter Blackstock has an effort at goal from just inside the box that misses to the right of the target.
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