Widnes and Castleford, the two suprise packets of Super League in 2014, will battle it out for a place at Wembley.
It is 21 years since Widnes were last in the Tetley's Challenge Cup final while Castleford's last visit to Wembley was in 1992, but one of the unfancied teams will reach the August 23 showpiece after they were paired together in the semi-final draw.
Leeds were drawn against Warrington in the other semi-final, which will be played on the weekend of August 9-10
Warrington coach Tony Smith, whose side secured a fifth semi-final in six years with a 46-10 rout of Bradford on Sunday, believes the appearance at Wembley of a "new" face will be good for the game.
"I don't really care who else is in there, as long as we're in there fighting for it but it's fantastic that there's going to be a fresh name at Wembley," Smith said.
"For too long there's been the same three or four and I think a fresh face is terrific for the game."
The Leeds-Warrington tie will be a repeat of the Wembley deciders in 2010 and 2012 as well as the 2012 Grand Final.