The Rhinos scored seven tries, four of them from wingmen Ryan Hall and Ben Jones-Bishop, to five in a breathtaking semi-final played in a wonderful atmosphere at Huddersfield's Galpharm Stadium to avenge their defeat by the Warriors at Wembley last August.
Leeds, who have not won the Cup since 1999, will seek to end their wait when they meet the winners of Sunday's tie between Huddersfield and Warrington at Wembley on August 25.
Saturday's victory came just six weeks after the Rhinos suffered a 50-8 mauling at home by Wigan but this time they managed to keep a tight rein on danger man Sam Tomkins, largely through the magnificent kicking of captain Kevin Sinfield, the man of the match.
Sinfield helped create four of his side's six first-half tries while the Rhinos were also well served by their other stalwarts Danny McGuire and Rob Burrow.
Zak Hardaker also went over twice for Leeds with Ryan Bailey claiming the other score.
George Carmont, Gareth Hock, Ben Flower, Sean O'Loughlin and Josh Charnley were Wigan's try-scorers.