Leeds, winners of Super League for four of the last five seasons, refused to give up their crown in Perpignan.
It was a classic play-off battle that could have gone either way, but two quick tries from Carl Ablett and Danny McGuire after the hour swung it the Rhinos' way and ended the Catalans' season. Even then, the champions' progress was not assured until McGuire's drop-goal three minutes from time.
The Dragons, with their partisan Catalan crowd behind them, were unrecognisable from the side that folded at Wigan last week and they led in the eighth minute. Jamie Peacock conceded the field position with a swinging arm at the head of Jason Baitieri and Clint Greenshields took Ian Henderson's pass, dummied to the outside and scored.
The Rhinos struggled to create in the opening half-hour. A run of three penalties their way, however, saw them exert some pressure and with two substitutions they went over.
Shaun Lunt opted to attack the blind-side on the last tackle of a set and that was enough to wrong-foot the defence for the 18-year-old Stevie Ward to stride through.Three minutes later it was Lunt again, backing up a break from Jamie Jones-Buchanan which looked to be made off a forward pass from Rob Burrow.
When Kevin Sinfield landed his second conversion Leeds looked well in. But right on half-time Damien Blanch intercepted from McGuire and went 90 metres, Scott Dureau converted from the touchline and Leeds' interval lead was cut to 12-10.
It looked a precarious lead and it was. After a high-tackle penalty that saw McGuire put on report, Dureau produced a pin-point kick to the corner and Blanch leapt to score his second. The tension boiled over in a series of set-tos as the Rhinos pummelled the French line, with try-saving tackles from Greenshields and Vincent Duport keeping them out.
Eventually they cracked, Sinfield going to dummy-half and putting in a clever little kick for Ablett to dive on to. A magnificent break from Ryan Bailey then set up McGuire and Leeds were on the way to the next round .
They still had nervous minutes to survive after Thomas Bosc went in with 11 minutes left. Catalans' coach, Trent Robinson, in his last match in charge, sent on a half-fit Leon Pryce, but Sinfield goaled after Jamal Fakir's high tackle.
Catalan Dragons: Greenshields; Blanch, Sa, Duport, Millard; Bosc, Dureau; Ferriol, Henderson, Casty, Menzies, Anderson, Baitieri. Substitutes used: Pryce, Mounis, Fakir, Paea.
Leeds: Hardaker; Jones-Bishop, Watkins, Ablett, Sinfield; McGuire, Hall; Kirke, Burrow, Peacock, Jones-Buchanan, Delaney, Bailey. Substitutes used: Clarkson, Griffin, Ward, Lunt. Referee: B Thaler (Wakefield).