Garry Monk's team selection backfired as Jamie Collins' unanswered penalty humbled Leeds and fired non-league Sutton into the fifth round of the FA Cup for the first time in their history.
Collins kept his cool from the spot (53) after a mix-up at the back saw Maxime Biamou upended as the part-timers, who famously ousted top-flight opposition back in 1989, made fresh memories at the expense of the Championship heavyweights.
The hosts had seen an early Roarie Deacon goal disallowed and been thwarted by a series of Marco Silvestri saves but the belated breakthrough was richly deserved and a young Leeds side - who saw Liam Cooper sent off late on - never really threatened to force even a face-saving replay.
Fans flooded Gander Green Lane's 3G pitch at the final whistle as Paul Doswell's National League side - 84 places below their opponents in the football pyramid - evoked the spirit of the team that toppled Coventry 28 years ago to embarrass their guests and join fellow underdogs Lincoln in the last 16.
Monk had warned of changes with a midweek game at Blackburn looming for his promotion-chasers and made 10 of them, Stuart Dallas the only man to keep his place from a Nottingham Forest victory that had lifted Leeds third and brought greater ambitions into sharper focus.
The visitors - who hit six when the sides last met here in 1970 - played keep-ball in the opening stages, feeling their way around the artificial surface in the driving rain, but they were saved by an early offside flag, Deacon racing onto Dan Spence's punt forward but dubiously ruled to have strayed by the time he blasted high into the net (6).
A long Nicky Bailey ball caused fleeting panic but Silvestri was forced into real action with 12 minutes on the clock when Deacon - who had scored in each previous rounds and was a menace once more - swivelled and drew a one-handed stop.
Bedsente Gomis was afforded a snapshot before Deacon cut inside again and took aim, only to find Cooper in the way, as amber shirts beat white ones to first and second balls.
It took Leeds until the half-hour to really test Ross Worner, Dallas glimpsing goal but seeing a curling effort deflected, yet Deacon sent Silvestri sprawling again and manager Doswell could well have felt hard done-by as he returned for the second half - steaming mug of tea in hand - without an advantage.
But the man not paid a Sutton salary and in the construction trade by day was punching the air just minutes after the restart following some shambolic Leeds defending.
Silvestre darted off his line to meet Biamou but succeeded only in colliding with a dithering Lewie Coyle, the Sutton forward falling to the the turf and referee Stuart Attwell pointing to the spot.
Collins stepped up and sent Silvestri the wrong way to spark wild celebrations on the old-style terraces as Monk looked on grimly.
The Leeds boss threw on Hadi Sacko and Kemar Roofe but Sutton rarely relented and the matchwinner went close to a second when he connected with a late free-kick at the back post.
Cooper's trip on Craig Eastmond moments earlier had earned him a second yellow card but Monk's men offered scant promise of wrestling back momentum before their afternoon got worse.
Attwell's whistle at the end prompted a joyous pitch invasion as humiliated Leeds made a hasty exit towards the tunnel, Sutton's triumph for a new generation ensuring that two non-league sides have got this far for the first time in the tournament's modern era.