Leeds are 80 minutes away from completing the treble after edging out reigning Super League champions St Helens 20-13 in a semi-final thriller at Headingley.
England winger Ryan Hall, whose last-second try at Huddersfield a week earlier earned the Rhinos a home semi-final, again made the crucial score 12 minutes from the end before centre Kallum Watkins added another in the final minute to break Saints hearts.
Leeds will now meet Wigan in the Grand Final at Old Trafford next Saturday in a repeat of the inaugural 1998 final won by Wigan thanks to Jason Robinson's solo try.
The outcome means that 37-year-old Jamie Peacock, who was heroic on his last appearance at Headingley, will get the chance to end his distinguished career on the big stage.
Captain Kevin Sinfield and long-serving prop Kylie Leuluai will also play their final games for the Rhinos before heading for rugby union and retirement respectively.
But spare a thought for St Helens, who overcame a series of injuries to play their part in a thoroughly absorbing contest that kept a 17,192 crowd spell-bound throughout.
It began badly for Saints when stand-off Jordan Turner dropped the ball from the kick-off but their defence looked assured from the start and they opened the scoring with a delightful opportunist try from hooker James Roby.
There was nothing on when Roby got the ball on the Leeds 30-metre but he evaded five would-be defenders on a weaving run that took him all the way to the line.
The score stung the Rhinos into action and they ought to have been level when winger Tom Briscoe followed up a break from deep inside his own half by centre Joel Moon to reach the corner only to lose the ball in Adam Swift's last-ditch tackle.
Saints extended their lead to 8-0 on 16 minutes with a Luke Walsh penalty after Danny McGuire was adjudged to be offside while intercepting the scrum-half's pass but the game continued to flow from end to end.
Leeds full-back Zak Hardaker accepted Watkins' offload to slide over for the 99th try of his career midway through the first half and Sinfield put over the conversion before drawing his side level with a penalty.
Walsh's drop goal on the stroke of half-time edged the visitors back in front but they were forced to hang onto their lead during a frantic start to the second half in which they were indebted to full-back Adam Quinlan for a tremendous tackle that brought a rampaging Hall to ground.
A limping Tom Makinson also stopped Hall in full flight before giving way to his leg injury and second rower Carl Ablett went preciously close before, at the other end Hardaker hauled down Saints prop Kyle Amor when in sight of the line.
Saints looked to have struck the decisive score on the hour when Hall lost the ball attempting to clear his lines, Jon Wilkin scooped it up and Turner sent Mark Percival racing over at the corner.
But Walsh was unable to add the conversion to give Leeds hope, which rose when Peacock, back on the field after just a seven-minute rest, stopped Roby on the line.
A 40-20 kick from Sinfield set up the position for Hall to take Moon's pass and force his way over for a try that brought his side to within a point and the skipper then kept his nerve to land the conversion that put the Rhinos in front for the first time.
Leeds could only breathe easily when Watkins picked up a loose ball to race over for their third try and Sinfield kicked his fourth goal.