Newport staged a dramatic late comeback to dump Leeds out of the FA Cup with a 2-1 victory at Rodney Parade.
County trailed for the majority of a full-blooded third-round affair after Gaetano Berardi's ninth-minute strike from distance found its way through.
But they levelled 14 minutes from time when Conor Shaughnessy sliced into his own net before Shawn McCoulsky's soaring header sent them into the fourth round for the first time since the 1978-79 season.
Leeds were then reduced to 10 men when substitute Samuel Saiz was immediately sent off in an off-the-ball incident.
The Sky Bet Championship visitors were much-changed - making nine alterations from the side held by Nottingham Forest on New Year's Day - and manager Thomas Christiansen's decision backfired in a frenzied finale.
Berardi was one of the two Leeds players to keep his place and he was influential as the visitors got off to the perfect start.
The Swiss defender took aim from 30 yards and his swerving drive possibly brushed the heel of Pierre-Michel Lasogga on the way through.
Berardi will clearly want to claim the goal, though, as he had not scored in his previous 101 Leeds appearances since joining from Sampdoria in the summer of 2014.
Leeds were straight out of the blocks and almost scored within 10 seconds when Jay-Roy Grot latched onto Hadi Sacko's knockdown.
Joe Day distinguished himself on that occasion, but the Newport goalkeeper had no answer to Berardi's long-range strike - deflection or not.
Newport, however, refused to be knocked out of their stride by that early setback, proof of how far League Two County have come under manager Mike Flynn.
Padraig Amond spun in the six-yard box and was only denied an equaliser by Mateusz Klich standing on the goal-line.
In a frantic contest, Leeds showed flashes of their greater pedigree, but the clearest chances belonged to Newport.
Skipper Joss Labadie planted a header straight at Andy Lonergan in the Leeds goal, and Amond's spectacular volleyed attempt flew just over.
The balance of play certainly did not reflect the 53 places between the two clubs on the league ladder and Amond improvised again to send an overhead kick wide at the start of the second half.
Leeds bolstered their back line by sending on Liam Cooper but there was concern when Frank Nouble arrived at the back post and fell under Lonergan's clumsy challenge.
Referee Mike Dean was not interested in penalty claims and Leeds went close to doubling their lead as Day pushed aside Lasogga's drive.
That set up a furious finale in which Newport were finally rewarded for their endeavour when the dangerous Nouble burst down the right for the umpteenth time and Shaughnessy diverted the ball into his own net.
Rodney Parade went wild and the ground was rocking again when substitute McCoulsky climbed above the Leeds defence from a corner in the final minute.
Saiz was then immediately banished and players from both sides had to be separated in the middle of the pitch.
It was a high-octane ending, but the win was no more than Newport deserved.