London Broncos won at Headingley for the first time since 2011
The London Broncos scored two late attempts to stun Leeds and force the Rhinos to a fourth consecutive Super League loss.
The Broncos had an 8-0 lead at halftime thanks to Kieran Dixon's goal and converted Jay Pitts' try.
But the hosts reversed the game through Richie Myler and Trent Merrin before Tom Briscoe crossed to extend their lead to 16-8.
However, Matty Fozard's score gave hope to the Londoners and Will Lovell tied the tie before Dixon's goal prevailed.
The visitors defended well to prevent Leeds from scoring in the first 20 minutes and scored the only try of the first half, after the Rhinos' defense spoiled Jordan Abdull's cross kick and Rhys Williams handed the ball in the game to allow Pitts to touch the ground.
The hosts were transformed after the break, while Myler showed his determination to force his way from 10 meters and that Merrin was introduced after the good work of Briscoe and Mikolaj Oledzki.
Briscoe then made his 300th career game, but a missed conversion of Tuimoala Lolohea proved crucial, as the Broncos made a remarkable comeback.
First of all, Fozard scored his own goal five minutes from time, and then Lovell kept his cool in the last chaotic match two minutes from London's first Headingley victory since 2011.
The promoted Broncos recorded their third victory and placed eighth, while Leeds remained eleventh after suffering their sixth loss in the campaign.
Leeds Rhinos head coach Dave Furner:
"The last six minutes have been very difficult.
"We did a very good job at half-time to reorient the group and we fought very well, we had control of the game, but the last six minutes hurt the group.
"That's not enough, we had opportunities in those first seven games and not taking them to some extent erased the team's confidence.
"We will have to get up ourselves, the season is long and there will be no white flag."
London Broncos head coach Danny Ward told BBC Radio London:
"We had to dig deep for that because we were shot in the second half and I did not think we played well.
"Leeds has quality players and dominated for great periods, but you should never doubt the resistance of our group.
"We had some difficult games and there were probably questions we were asked, but coming to Headingley and winning gives the boys confidence."
"We are satisfied with where we are, but there are many areas to repair and work on, we can not let ourselves be carried away."
Leeds: Walker, Briscoe, Newman, Hurrell, Handley, Lolohea, Myler, Peteru, Parcell, Oledzki, Merrin, Ferres, Sutcliffe.
replacements: Cuthbertson, Jones-Buchanan, Donaldson, Holroyd.
London Broncos: Walker, Dixon, Morgan, Kear, Williams, Abdull, Cunningham, Battye, Pelissier, Butler, Pitts, Yates, Davies.
replacements: Lovell, Fozard, Richards, Mason.
Arbitrator: Chris Kendall.