A brace from Billy Paynter inspired Swindon to a convincing win, lifting the club up to second in the League One table and forcing former leaders United down to fourth.
Charlie Austin put the seal on the result with a second-half header, piling pressure onto manager Simon Grayson and his players.
A lively first half saw countless chances and both sides could have held the lead at half-time.
Paynter, Austin and Danny Ward all went close for Swindon but Leeds right-back Andrew Hughes had the best opportunity, shooting against goalkeeper David Lucas from three yards out.
Jermaine Beckford also saw a glancing header saved but Swindon grabbed the lead two minutes before the break when Paynter met Jon-Paul McGovern's cross with a volley which flew inside Shane Higgs' near post.
It took a brilliant save from Higgs to deny Austin a second goal before the break but Paynter struck three minutes into the second half to leave Swindon in firm control, and Austin's 55th-minute header confirmed United's crushing defeat.
Charlie Austin put the seal on the result with a second-half header, piling pressure onto manager Simon Grayson and his players.
A lively first half saw countless chances and both sides could have held the lead at half-time.
Paynter, Austin and Danny Ward all went close for Swindon but Leeds right-back Andrew Hughes had the best opportunity, shooting against goalkeeper David Lucas from three yards out.
Jermaine Beckford also saw a glancing header saved but Swindon grabbed the lead two minutes before the break when Paynter met Jon-Paul McGovern's cross with a volley which flew inside Shane Higgs' near post.
It took a brilliant save from Higgs to deny Austin a second goal before the break but Paynter struck three minutes into the second half to leave Swindon in firm control, and Austin's 55th-minute header confirmed United's crushing defeat.
Shane Higgs: Questions will be asked about Paynter's first strike, which beat Higgs at his near post, but his save from Austin was brilliant and he could not have stopped the second or third goals...6/10
Andrew Hughes: The chance he missed will haunt him, as will his slip before Swindon's opener, but he covered plenty of ground and was not guilty of throwing in the towel...6/10
Richard Naylor: Even before their first concession, Leeds were showing signs of frailty at the back, and Austin's cheap header summed up a grim day for Naylor and the defence around him...4/10
Neill Collins: His partnership with Naylor earned acclaim at Norwich but Collins lacked the same conviction against Swindon and the pair were no match for Austin and Paynter...5/10
Shane Lowry: Another satisfactory display at left-back and he got forward with more vigour, almost laying on a goal for Hughes. Looked less comfortable after switching to the centre of defence...6/10
Michael Doyle: United's midfield were in control until Paynter's match-turning finish two minutes before the break. After that, Doyle failed to give the defence behind him the protection it needed...5/10
Jonathan Howson: His performance in the first half was his sharpest for a while and he and Hughes worked the right channel to good effect. But three quick goals shattered his influence...6/10
Neil Kilkenny: Played his part in a purposeful display for 43 minutes but Kilkenny had little chance of instigating a fightback once the sting was taken out of the game...6/10
Robert Snodgrass: A mixed bag from Snodgrass who made an impression in periods of the game but was wholly ineffective in others. Missed two of United's better chances, one in each half...5/10
Mike Grella: His hold-up play was intelligent, his effort in a hopeless situation was an example to others and he was able to walk out of Elland Road with his head held high...7/10
Jermaine Beckford: It was easy to forget that League One's player of the year was on the pitch. Saw next to nothing of the ball and had the look of a passenger in comparison to the tireless Grella...4/10
Substitutes: Max Gradel (for Doyle, 60)...6/10
Ben Parker (for Naylor, 60)...5/10
Paul Dickov (for Grella, 75)...5/10
Not used: Casper Ankergren, Leigh Bromby, Sanchez Watt, Bradley Johnson.
Andrew Hughes: The chance he missed will haunt him, as will his slip before Swindon's opener, but he covered plenty of ground and was not guilty of throwing in the towel...6/10
Richard Naylor: Even before their first concession, Leeds were showing signs of frailty at the back, and Austin's cheap header summed up a grim day for Naylor and the defence around him...4/10
Neill Collins: His partnership with Naylor earned acclaim at Norwich but Collins lacked the same conviction against Swindon and the pair were no match for Austin and Paynter...5/10
Shane Lowry: Another satisfactory display at left-back and he got forward with more vigour, almost laying on a goal for Hughes. Looked less comfortable after switching to the centre of defence...6/10
Michael Doyle: United's midfield were in control until Paynter's match-turning finish two minutes before the break. After that, Doyle failed to give the defence behind him the protection it needed...5/10
Jonathan Howson: His performance in the first half was his sharpest for a while and he and Hughes worked the right channel to good effect. But three quick goals shattered his influence...6/10
Neil Kilkenny: Played his part in a purposeful display for 43 minutes but Kilkenny had little chance of instigating a fightback once the sting was taken out of the game...6/10
Robert Snodgrass: A mixed bag from Snodgrass who made an impression in periods of the game but was wholly ineffective in others. Missed two of United's better chances, one in each half...5/10
Mike Grella: His hold-up play was intelligent, his effort in a hopeless situation was an example to others and he was able to walk out of Elland Road with his head held high...7/10
Jermaine Beckford: It was easy to forget that League One's player of the year was on the pitch. Saw next to nothing of the ball and had the look of a passenger in comparison to the tireless Grella...4/10
Substitutes: Max Gradel (for Doyle, 60)...6/10
Ben Parker (for Naylor, 60)...5/10
Paul Dickov (for Grella, 75)...5/10
Not used: Casper Ankergren, Leigh Bromby, Sanchez Watt, Bradley Johnson.