Leeds Rhinos 32
Tries: Hall 2, McGuire 2, Webb
Goals: Sinfield 6
St Helens 28
Tries: Wellens, Cunningham, Meli, Gidley, Graham
Goals: Foster 4
Saints had beaten Leeds in their three previous Cup meetings, but they were dealt a huge blow as they lost influential half-back Leon Pryce to a neck injury that could keep him out for the rest of the season.
In a ten minute spell just before the break St Helens took control as they scored three unanswered tries to lead 18-8. Firstly Paul Wellens turned his way over the line and Kerion Cunningham scored his trademark try from dummy half before on half time Francis Meli intercepted a wayward pass from Greg Eastwood to stroll away and score underneath the posts.
Needing to reply first after the break Leeds made the most of a Jon Wilkin knock-on to send Hall in at the corner, Sinfield's conversion bringing them back to within four points. Gidley restored Saints advantage by scoring from close range.
However, the Rhinos roared back and hit St Helens with a two try burst in four minutes to re-take the lead 26-22. Danny McGuire juggled a pass from Keith Senior to get Leeds back in it and a brilliant pass from hooker Danny Buderus sent Webb away.
The game was set up in the last ten minutes. James Graham scored from close range to regain the lead but there was to be one more twist as Jamie Peacock's reverse pass to McGuire who cut through the Saints defence and dive over, with Sinfield's conversion completing the win as the Rhinos return to Wembley for the first time since they won the last final at the Old Stadium in 1999.
Tries: Harrison, L Anderson 3, King, Riley, Briers, Myler, Clarke
Goals: Westwood 7, Briers, Myler
Catalans Dragons 12
Tries: Greenshields 2
Goals: Bosc 2
Holders Warrington Wolves booked a return visit to Wembley by demolishing Catalans Dragons at Stobart Stadium Widnes.
After defeating Warrington two weeks ago Catalans came into this game full of confidence but there was not going to be any upset as the Wolves ruthlessly put the French-side to the sword.
Ben Harrison took four defenders over the line to score the opening try on six minutes and five minutes later Ryan Atkins got the ball to Louis Anderson to double their advantage.
The second half was much the same as the first as the Wolves ran in a further five tries to make it nine for the game.
Anderson went on to complete his hat-trick, Lee Briers, Richie Myler and Jon Clarke also got in on the try-scoring act in a comfortable Warrington victory.
Greenshields did manage to score the final try of the match but his team was never in it. So Warrington Wolves will now play Leeds on Saturday 28th August at Wembley in a repeat of the 1936 Cup Final.