Huddersfield made a piece of club history by winning at Headingley for the first time since 1960 and showing that it is they and not Leeds who are the genuine title contenders.
The result puts the Giants a point clear at the top of the Super League table.
Dale Ferguson was the unexpected try-scoring hero, but Huddersfield were superior in all departments, particularly at half-back where Kevin Brown and Danny Brough ruled the roost.
In all the years since Huddersfield last won here it can only have been very rarely that they had come to Headingley as definite favourites. After a scrappy opening phase characterised by handling errors on both sides, the Giants set about justifying that status in style.
Leeds' problems began when they were penalised for holding down Jermaine McGillvary and continued when the porous defence that has undermined them all season allowed Ferguson to stroll over without a hand laid upon him in anger.
Three minutes later Darrell Griffin's ball out of the tackle exposed the Rhinos again, Scott Grix chiming perfectly into the line to take Brown's pass and send McGillvary over.
The Giants then made it 20-0 just after the half-hour. Brown was heavily involved again, slipping his pass out of a tackle, but the ease with which Ferguson was allowed to saunter through was scandalous.
The Rhinos came off at half-time to a chorus of booing. Given their lack of resolve in the first 40 minutes they could hardly have been surprised, and their frustration showed in the outbreak of fighting at the start of the second half that saw Ryan Bailey sent off along with the Giants' Luke O'Donnell.
The Rhinos at least prevented a whitewash when Keith Senior's break down the left and pass to Rob Burrow produced a try that Kevin Sinfield goaled. But any glimmer of hope was snuffed out four minutes later by Shaun Lunt pouncing on a loose ball for another try. Then, with numbers on both teams depleted, Luke Robinson scored the fifth Giants try and right on time Lunt grabbed a second.
The Giants coach, Nathan Brown, called the officials' handling of the fight "disgraceful". "When key players are taken out off the ball, they should be sent off. Instead, they send Luke O'Donnell off for doing nothing, when he should have laid Bailey out cold."
Leeds: Webb; Watkins, Delaney, Senior, Hall; Sinfield, Burrow; Bailey, Buderus, Leuluai, Jones-Buchanan, Clarkson, Kirke. Substitutes used Cross, McShane, Hauraki, Burgess.
Huddersfield: Grix; McGillvary, Cudjoe, Lawrence, Simpson; Brown, Brough; Crabtree, Robinson, Griffin, Gilmour, Ferguson, O'Donnell. Substitutes used Faiumu, Lunt, Patrick, Horne.
Referee: B Thaler (Wakefield).
*Wigan's coach Michael Maguire has confirmed he is to leave the club at the end of the season. The 37-year-old Australian has, as was widely expected, decided to accept an offer to join Australian side South Sydney from 2012. Maguire who won the Super League at the first attempt last season, revealed the switch after his side's 28-16 win at Hull KR last night.