Ed Upson's late header fired Yeovil Town into the League One play-off final at the expense of Sheffield United.
The Glovers, trailing 1-0 from Friday's semi-final first leg, levelled the tie inside five minutes from Kevin Dawson's slotted finish following Upson's pass.
Jamie Murphy hit the bar for the Blades in an end-to-end encounter.
But Upson won it for Yeovil in the dying stages, heading home Paddy Madden's cross five minutes from time to continue the Blades' play-off woe.
Sheffield United have now failed to go up in all seven play-off campaigns they have been involved in. Last season, they lost on penalties after a goalless draw with Huddersfield at Wembley.
Sheffield United entered this play-off campaign having failed in each of the previous six end-of-season finales they have been involved in - and this was to end similarly.
Yeovil's only previous experience of the play-offs at this level also ended in failure, with a Wembley final defeat by Blackpool in 2007.
But, on their way to Wembley, they overturned a 2-0 first-leg deficit to stun Nottingham Forest 5-2 at the City Ground and, knowing an early goal could make all the difference here, they started like a train.
A succession of Jamie McAllister corners culminated in Dan Burn's header flashing wide of the far post but that miss was just a warning.
Upson found himself in space on the edge of the area and his brilliant pass found Dawson, drifting in from the right-hand side, the Irishman duly applying the finish for only his third goal in English football.
United needed a response of sorts and Callum McFadzean, who also caught the eye in Friday night's first leg, was unsurprisingly the man to provide it.
Having already had a half-hearted penalty appeal turned down, the 19-year-old jinked his way across the box only to see his shot blocked at source, before Michael Doyle's fizzing effort on the follow-up stung the fingers of Marek Stech.
Gary Johnson, who returned to Huish Park as manager in January 2012, guided the Somerset club from the Conference to League One in his previous spell in charge - and is now trying to win promotion to English football's second tier.
Joe Edwards then had a good chance for Yeovil on the break, only for Blades keeper George Long to keep out his angled shot, before Joe Ironside's effort from almost an identical position at the other end was blocked by Stech moments later.
With the tie evenly poised, Murphy came within centimetres of giving the Blades an all-important lead.
The Scotsman, who arrived from Motherwell in January, cut inside onto his right foot but could only send his curling effort against the bar.
It was the final clear opportunity of a first half that had been fast and frantic and any fears the second would not continue in the same manner were quickly distinguished.
United striker Chris Porter could only find the side-netting when well placed after his first effort was blocked, and then Madden, presented with the League One golden boot before kick-off, tamely shot straight at Long from 12 yards.
Madden then had an even better chance when Luke Ayling's right-wing cross evaded everyone to leave the Irishman with the goal at his mercy at the far post, but he headed high and wide.
With the tie seemingly destined for extra time, James Hayter wasted another excellent opportunity, heading wide from Sam Foley's left-wing cross, but that was not to be the Glovers' last chance.
Madden crossed for Upson from the right and the midfielder rose unmarked to steer the ball back across goal beyond Long.
VIEW FROM THE DRESSING ROOM
Yeovil Town manager Gary Johnson told BBC Somerset:
Johnson 'proud' of Yeovil team
"It's great all the preparation and planning came off for us, even down to the last two minutes.
"We haven't won it yet, but we have to allow our club to celebrate getting to Wembley, our fans wouldn't allow us not to. We now have a great opportunity.
"I don't think anybody could say we didn't deserve to go through over the two games.
"When the book comes out we'll have to look at the last chapter to see how we get on at Wembley."
Yeovil's Kevin Dawson, scorer of the Glovers' first goal, told BBC Somerset:
"This means everything to the club. I can't explain what I'm feeling. It's the best feeling I've ever had in my life, unreal.
"We're now 90 minutes away from the Championship and that's where we want to be. I've never been to Wembley, so I can't wait.
"I knew if I made the run Ed Upson would find me. I'm delighted it went in.
"We didn't want extra time. I was in total shock when Ed's goal went in."
Blades caretaker boss Chris Morgan told BBC Radio Sheffield:
"It's cruel. I have said to the players that we don't deserve that, but sometimes you don't get what you deserve. It's the worst way to lose, but we have to take it on the chin and come back to mount another challenge.
"We made a great start on Friday night and got our noses in front. And, although we're disappointed to concede after five minutes today, I genuinely thought that once they scored they went on the back foot.
"As the game grew, I thought, with the players we had on the pitch, we might sneak one. Did we create enough to win it on the day? Probably not, but the players we've got have given us everything.
"I'd love to lead the team next season. Whether that changes after today, I don't know, I can't answer that."
Full Time The game is over, as the referee blows his whistle.
Marek Stech restarts play with the free kick.
90:00 +3:15 Booking
Booking Kevin McDonald is cautioned.
Dave Kitson concedes a free kick for a foul on Byron Webster.
90:00 +2:01 Substitution
Substitution (Yeovil) makes a substitution, with Richard Hinds coming on for James Hayter.
The ball is delivered by Harry Maguire, Byron Webster manages to make a clearance.
Harry Maguire challenges Paddy Madden unfairly and gives away a free kick. Direct free kick taken by Marek Stech.
Jamie Murphy delivers the ball, save made by Marek Stech.
The ball is swung over by Ryan Flynn, clearance by Edward Upson.
The ball is sent over by Paddy Madden, Shot by Sam Foley from deep inside the penalty area misses to the right of the goal.
Dave Kitson challenges Byron Webster unfairly and gives away a free kick. Direct free kick taken by Luke Ayling.
Substitution Ryan Flynn replaces Callum McFadzean.
Centre by Paddy Madden,
The assist for the goal came from Paddy Madden.
84:16 Goal scored
Goal! - Edward Upson - Yeovil 2 - 0 Sheff Utd Edward Upson grabs a headed goal from inside the area. Yeovil 2 (2)-(1) 0 Sheff Utd.
James McAllister sends in a cross, Harry Maguire makes a clearance.
Headed effort from deep inside the area by James Hayter misses to the right of the target.
James Hayter concedes a free kick for a foul on Harry Maguire. Direct free kick taken by Harry Maguire.
Effort from outside the penalty box by Edward Upson goes wide right of the target.
Corner taken by James McAllister from the left by-line, Harry Maguire manages to make a clearance.
The ball is delivered by Edward Upson.
Jamie Murphy crosses the ball.
Foul by Kevin Dawson on Kevin McDonald, free kick awarded. George Long takes the direct free kick.
The official flags Callum McFadzean offside. Free kick taken by Marek Stech.
Harry Maguire has a headed effort at goal from just inside the penalty area that misses to the left of the goal.
Corner taken by Jamie Murphy, Luke Ayling makes a clearance.
Free kick awarded for an unfair challenge on Danny Higginbotham by James Hayter. Free kick taken by George Long.
Paddy Madden produces a cross, clearance by Matthew Hill.
Matthew Hill takes a shot. Save made by Marek Stech.
Dan Burn concedes a free kick for a foul on Dave Kitson. Free kick taken by Michael Doyle.
Substitution Joe Ironside leaves the field to be replaced by Dave Kitson.
Unfair challenge on Sam Foley by Callum McFadzean results in a free kick. Edward Upson delivers the ball from the free kick right-footed from left wing.
The assistant referee flags for offside against Kevin Dawson. Direct free kick taken by George Long.
Danny Higginbotham fouled by Joe Edwards, the ref awards a free kick. Michael Doyle takes the free kick.
Centre by Sam Foley.
Substitution Danny Higginbotham is brought on as a substitute for Darryl Westlake.
Jamie Murphy produces a left-footed shot from just outside the area that goes harmlessly over the target.
Paddy Madden is caught offside. George Long restarts play with the free kick.
The ball is crossed by Luke Ayling, Close range header by Paddy Madden goes over the crossbar.
A cross is delivered by Jamie Murphy, save by Marek Stech.
Free kick awarded for a foul by Kevin Dawson on Michael Doyle. Free kick taken by George Long.
Corner taken by James McAllister, clearance made by Kevin McDonald.
Effort from inside the six-yard box by Chris Porter goes wide left of the target.
The second half begins.
45:00 +1:04 Half time
Half Time The first half comes to an end.
Matthew Hill delivers the ball, Byron Webster manages to make a clearance.
Jamie Murphy takes a shot. Inswinging corner taken by Darryl Westlake from the left by-line, Close range header by Harry Maguire goes over the bar.
James McAllister fires a strike on goal direct from the free kick, Corner taken right-footed by Edward Upson from the left by-line, Headed effort from inside the box by Dan Burn misses to the right of the target.
Booking Harry Maguire goes into the referee's book.
Free kick awarded for a foul by Harry Maguire on Paddy Madden.
Callum McFadzean gives away a free kick for an unfair challenge on James McAllister. Free kick taken by James McAllister.
Joe Ironside is caught offside. Free kick taken by Marek Stech.
James Hayter fouled by Matthew Hill, the ref awards a free kick. James McAllister takes the direct free kick.
Kevin Dawson is caught offside. George Long takes the indirect free kick.
Jamie Murphy takes a shot.
The ball is delivered by Jamie Murphy.
James McAllister delivers the ball, Luke Ayling produces a right-footed shot from the edge of the box and misses to the right of the goal.
Jamie Murphy takes a shot. Save made by Marek Stech.
The ball is crossed by Callum McFadzean, Paddy Madden makes a clearance.
Paddy Madden is flagged offside by the assistant referee. George Long restarts play with the free kick.
The ball is swung over by Darryl Westlake, blocked by Luke Ayling.
Michael Doyle crosses the ball, Paddy Madden manages to make a clearance.
Joe Edwards takes a shot. Save by George Long.
Unfair challenge on Joe Edwards by Michael Doyle results in a free kick. James McAllister restarts play with the free kick.
Callum McFadzean takes a shot. Blocked by Byron Webster. Michael Doyle takes a shot. Marek Stech makes a comfortable save. Outswinging corner taken right-footed by Darryl Westlake from the left by-line, clearance by Dan Burn.
Free kick awarded for a foul by Edward Upson on Kevin McDonald. Harry Maguire restarts play with the free kick.
Effort on goal by Kevin McDonald from outside the area goes harmlessly over the bar.
Unfair challenge on Joe Ironside by Byron Webster results in a free kick. Darryl Westlake takes the free kick.
Sam Foley fouled by Darryl Westlake, the ref awards a free kick. James McAllister takes the free kick.
Effort on goal by Kevin McDonald from long range goes harmlessly over the target.
Kevin McDonald takes a shot. Corner taken right-footed by Darryl Westlake from the left by-line, James Hayter manages to make a clearance. The ball is crossed by Kevin McDonald, Dan Burn makes a clearance.
Booking Kevin Dawson booked.
James Hayter provided the assist for the goal.
5:06 Goal scored
Goal! - Kevin Dawson - Yeovil 1 - 0 Sheff Utd Kevin Dawson finds the back of the net with a goal from deep inside the penalty box to the bottom right corner of the goal. Yeovil 1 (1)-(1) 0 Sheff Utd.
Luke Ayling delivers the ball, Corner taken by James McAllister, Dan Burn has a headed effort at goal from close range which goes wide left of the target.
The ball is delivered by Paddy Madden, clearance made by Matthew Hill.
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