A hot-tempered contest at Franklin's Gardens
Tom Wood scored a dramatic late try to complete a Northampton Saints comeback and deny Leicester Tigers a tenth straight Premiership Final.
In a hot-tempered contest at Franklin's Gardens, Manu Tuilagi and Ben Youngs each dotted down to put the Tigers in control at the break.
However, George North crashed over near the end and Wood completed the job in the dying seconds to ensure 14-man Northampton avenged their defeat in last year's final.
Following a see-saw opening to the tie Toby Flood - starting in place of Owen Williams - soon sent a penalty over to give Leicester the lead after ten minutes.
Saints bounced back immediately and Youngs was forced to chase a pinpoint kick towards his own corner flag and scramble the ball into touch.
Northampton pounced and some quick thinking in the corner from scrumhalf Kahn Fotuali'i saw him steal a run on the line, only for Mathew Tait's last-ditch tackle to prevent the score.
The home side thought they had scored from the resulting lineout, as captain Phil Dowson crossed over, but referee JP Doyle ruled there had been an infringement at the set piece.
Not to be deterred, Saints soon broke the Leicester line through Luther Burrell and, once Stephen Myler had sent a penalty to the corner, they continued to threaten from the lineout.
Leicester cleared but the hosts' tails were up, coming once again and after more smart work from Fotuali'i the scrumhalf won his side a penalty, allowing Myler to level the scores.
The parity wouldn't last long, however, as incisive running from Flood and then Tait allowed Tuilagi to cross over after 25 minutes - and Flood duly converted.
Niki Goneva saw yellow on half an hour for illegal use of his feet at the breakdown and Myler's penalty reduced the arrears to 10-6 but the numerical disadvantage didn't appear to deter the Tigers who were soon further ahead.
Scrumhalf Youngs nipped sharply around the ruck to cross over from close range and Flood made it three from three to open up an 11-point lead at the break.
Leicester escaped a messy lineout four minutes into the second half and they were soon down to 14 again, after Dan Bowden was sin-binned for an illegal tackle on Tom Collins - Myler's ever-accurate boot reduced the deficit.
Amidst further Saints pressure tempers boiled over and Tom Youngs saw yellow for grappling with Salesi Ma'afu, who was shown a red card for punching the Tigers hooker.
The contest enjoyed a much-needed quiet period but it was Saints who popped up with the pivotal moment, North piling onto a Lee Dickson pass to crash over on 65 minutes and Myler converting.
Saints were now just one point adrift but replacement Williams widened that gap slightly seven minutes from time with his first penalty, after Northampton were punished at the lineout.
With a kickable penalty four minutes from time Myler opted for the corner and it paid off when, after a string of high-pressure phases, Wood flew over the whitewash to grab the lead for Northampton.
Myler's conversion was wide but it didn't matter as time ran out and Saints progressed, with either Saracens or Harlequins waiting at Twickenham.
For Northampton Saints:
Tries: North, Wood
Cons: Myler 2
Pens: Myler 3
For Leicester Tigers:
Tries: Tuilagi, B Youngs
Cons: Flood 2
Pens: Flood, Williams
Yellow Cards: Vereniki Goneva (Leicester Tigers, 30 mins - Cynical infringement), Dan Bowden (Leicester Tigers, 45 mins - Dangerous tackle), Tom Youngs (Leicester Tigers, 55 mins - Foul play)
Red Card: Salesi Ma'afu (Northampton Saints, 55 mins, Foul play)
Northampton Saints: 15 Ben Foden, 14 Jamie Elliott, 13 George Pisi, 12 Luther Burrell, 11 George North, 10 Stephen Myler, 9 Kan Fotuali'i, 8 Sam Dickinson, 7 Phil Dowson (captain), 6 Tom Wood, 5 Courtney Lawes, 4 Samu Manoa, 3 Salesi Ma'afu, 2 Mike Haywood, 1 Alex Waller
Replacements: 16 Ross McMillan, 17 Alex Corbisiero, 18 Tom Mercey, 19 Christian Day, 20 Calum Clark, 21 Lee Dickson, 22 James Wilson, 23 Tom Stephenson
Leicester Tigers: 15 Mathew Tait, 14 Niall Morris, 13 Manu Tuilagi, 12 Dan Bowden, 11 Vereniki Goneva, 10 Toby Flood, 9 Ben Youngs, 8 Jordan Crane, 7 Julian Salvi, 6 Jamie Gibson, 5 Ed Slater (captain), 4 Louis Deacon, 3 Logovi'i Mulipola, 2 Tom Youngs, 1 Marcos Ayerza
Replacements: 16 Neil Briggs, 17 Tom Bristow, 18 Fraser Balmain, 19 Graham Kitchener, 20 Steve Mafi, 21 David Mele, 22 Owen Williams, 23 Adam Thompstone
Referee: JP Doyle
Assistant Referees: Nigel Carrick, Paul Dix
TMO: Rowan Kitt