A late header from Chris Porter sent Sheffield United into the League One play-off final at Stevenage's expense.
Porter came closest to opening the scoring in a drab first period, only for Boro goalkeeper Chris Day to pull off a fine save.
The visitors improved after the break and Luke Freeman and Scott Laird forced home keeper Steve Simonsen into action.
But, with time running out, Porter won it with a far post header from Matt Lowton's cross.
The Blades, relegated from the second tier last season, will now return to Wembley for the first time since losing in the 2009 Championship play-off final.
Returning to Bramall Lane after the goalless first leg, the hosts almost got off to the perfect start, but Porter's close-range header was spectacularly saved by Day.
That early chance was a rare bright spot in an otherwise attritional first period, with both teams seemingly putting more emphasis on defence than opening the scoring.
The two lone front men, Porter for the hosts and Patrick Agyemang for the visitors, were too often isolated against resilient defences with both sets of midfielders struggling to find space and creativity in a congested middle.
As per the first leg, it was Luke Freeman who looked most likely to force the issue for Boro, but he too cut a remote and frustrated figure by the interval.
Both managers will have been grateful for the sound of the half-time whistle, particularly visiting boss Gary Smith, whose side failed to register a single attempt on Simonsen's goal.
The second half was a distinct improvement on the first and United went close three times in quick succession.
First, Ryan Flynn's shot from inside the area was blocked four yards out, then Porter's cross was fired wide by Lee Williamson at the near post before Flynn lashed a half-volley just wide.
This roused Boro, and Freeman linked up well with Scott Laird before embarking on a mazy run that culminated in his side's first shot of the night, easily saved by Simonsen.
Stevenage began to sense they could cause an upset and another Freeman run ended with a super save by Simonsen from a well-struck Laird effort before Michael Bostwick fired a free-kick straight at the keeper from 30 yards out.
With home fans becoming restless, both Matt Hill and Stephen Quinn went close before Porter settled the contest and United nerves with a towering header at the far post from Lowton's excellent centre.
Boro sub Chris Beardsley forced a save from Simonsen with a header from 18 yards but their dream of three successive promotions came to an end with Danny Wilson's side holding out to spark scenes of wild jubilation as home fans rushed on to the pitch at the final whistle.
The Blades will face either Huddersfield or MK Dons in the final on Saturday, 26 May.
VIEWS FROM THE DRESSING ROOM
Sheffield United manager Danny Wilson told BBC Radio Sheffield:
"(I feel) very proud, but we were pushed to the limit tonight.
"Although we've played very well I think some of the football we've played has been outstanding. We had a real game plan and the lads carried it through to the letter.
"And thankfully we've come up with a great goal at the end to win it."
Full Time The referee blows his whistle to end the game.
Unfair challenge on Jamaal Lascelles by Chris Porter results in a free kick. Direct free kick taken by Scott Laird.
Centre by John Mousinho, Chris Beardsley takes a shot. Comfortable save by Steve Simonsen.
Inswinging corner taken from the left by-line by John Mousinho, clearance by Neill Collins.
Substitution Craig Reid is brought on as a substitute for Joel Byrom.
Right-footed shot by Lawrie Wilson went wide of the left-hand upright.
The assist for the goal came from Matthew Lowton.
84:08 Goal scored
Goal - Chris Porter - Sheff Utd 1 - 0 Stevenage Chris Porter finds the net with a headed goal from inside the six-yard box. Sheff Utd 1 (1)-(0) 0 Stevenage.
The ball is sent over by Matthew Lowton,
Michael Bostwick takes a long range shot harmlessly clearing the crossbar.
Stephen Quinn takes a shot. Save made by Chris Day.
Effort from 35 yards by Matthew Hill went wide of the right-hand post.
The ball is delivered by Ryan Flynn, Mark Roberts makes a clearance.
Matthew Hill sends in a cross, clearance made by Jon Ashton.
The ball is delivered by Stephen Quinn, Luke Freeman gets a block in. Matthew Lowton takes a shot. Mark Roberts gets a block in.
Ryan Flynn concedes a free kick for a foul on Luke Freeman. Michael Bostwick fires a strike on goal direct from the free kick, save made by Steve Simonsen.
Outswinging corner taken from the left by-line by Joel Byrom.
Booking The referee shows Matthew Lowton a yellow card for unsporting behaviour.
Luke Freeman takes a shot. Nick Montgomery gets a block in. Scott Laird takes a shot. Steve Simonsen makes a save.
The ball is delivered by Matthew Lowton.
Corner taken by Lee Williamson from the right by-line played to the near post, Michael Bostwick manages to make a clearance.
Lee Williamson produces a cross, Joel Byrom gets a block in.
Foul by Michael Bostwick on Chris Porter, free kick awarded. Strike on goal comes in from Lee Williamson from the free kick.
The ball is crossed by Stephen Quinn, Jon Ashton makes a clearance.
Matthew Hill produces a cross, blocked by Jamaal Lascelles.
Unfair challenge on Chris Porter by Mark Roberts results in a free kick. Free kick taken by Lee Williamson.
Centre by Luke Freeman, clearance by Matthew Hill.
Matthew Lowton crosses the ball, Jon Ashton manages to make a clearance.
Inswinging corner taken left-footed by Luke Freeman, clearance by Chris Porter.
Substitution Chris Beardsley on for Patrick Agyemang.
Stephen Quinn produces a left-footed shot from just outside the box that goes wide left of the goal.
Centre by Matthew Lowton, clearance made by Mark Roberts.
John Mousinho is penalised for a handball. Harry Maguire takes the direct free kick.
Luke Freeman takes a shot. Save by Steve Simonsen.
Substitution John Mousinho on for Robin Shroot.
Ryan Flynn produces a right-footed shot from outside the penalty box and misses right.
The ball is sent over by Stephen Quinn, Jamaal Lascelles makes a clearance.
Chris Porter sends in a cross, Lee Williamson has an effort at goal from close range which goes wide right of the goal.
The offside flag is raised against Patrick Agyemang. Neill Collins takes the indirect free kick.
Lee Williamson produces a cross, Ryan Flynn takes a shot. Lawrie Wilson gets a block in.
Matthew Lowton delivers the ball, Michael Bostwick manages to make a clearance.
Centre by Lee Williamson, Ryan Flynn takes a shot. Blocked by Jon Ashton.
The second half kicks off.
Substitution Nick Montgomery replaces Kevin McDonald.
45:00 +2:26 Half time
Half Time The ref blows to end the first period.
The ball is crossed by Ryan Flynn.
Shot from long range by Lee Williamson misses to the right of the goal.
The ball is crossed by Patrick Agyemang.
Ryan Flynn concedes a free kick for a foul on Robin Shroot. Joel Byrom takes the direct free kick.
Stephen Quinn crosses the ball, Jon Ashton makes a clearance.
Jamaal Lascelles delivers the ball, clearance by Kevin McDonald.
Handball decision goes against Lawrie Wilson. Matthew Hill takes the direct free kick.
The ball is delivered by Scott Laird, Matthew Lowton manages to make a clearance.
Michael Doyle takes a shot. Michael Bostwick gets a block in.
Lee Williamson decides to take a short corner.
A cross is delivered by Matthew Hill, Jon Ashton makes a clearance.
Free kick awarded for a foul by Lawrie Wilson on Ryan Flynn. Neill Collins restarts play with the free kick.
The ball is crossed by Joel Byrom, clearance made by Harry Maguire.
Free kick awarded for a foul by Luke Freeman on Lee Williamson. Free kick taken by Matthew Lowton.
Unfair challenge on Joel Byrom by Matthew Lowton results in a free kick. Chris Day restarts play with the free kick.
Corner taken right-footed by Lee Williamson, clearance made by Jon Ashton.
Ryan Flynn sends in a cross, Jon Ashton makes a clearance.
Matthew Hill sends in a cross.
The ball is delivered by Matthew Lowton, clearance by Jon Ashton.
A cross is delivered by Matthew Lowton, clearance made by Mark Roberts.
Centre by Ryan Flynn.
Kevin McDonald takes a shot. Michael Bostwick gets a block in.
Michael Doyle produces a cross.
Mark Roberts concedes a free kick for a foul on Chris Porter. Lee Williamson restarts play with the free kick.
A cross is delivered by Lawrie Wilson, clearance by Neill Collins.
Matthew Hill crosses the ball, Chris Day makes a save.
Stephen Quinn sends in a cross, Jamaal Lascelles makes a clearance.
The ball is swung over by Matthew Lowton, blocked by Scott Laird.
A cross is delivered by Stephen Quinn, Jon Ashton manages to make a clearance.
Short corner taken by Lee Williamson, Centre by Matthew Lowton, clearance made by Jon Ashton. Ryan Flynn produces a right-footed shot from just outside the penalty area that goes harmlessly over the target.
The ball is swung over by Matthew Hill, Chris Porter takes a shot. Save by Chris Day.
Harry Maguire crosses the ball, clearance made by Jon Ashton.
The ball is swung over by Kevin McDonald, blocked by Joel Byrom.
Foul by Luke Freeman on Lee Williamson, free kick awarded. Lee Williamson restarts play with the free kick.
Corner taken left-footed by Joel Byrom, Matthew Lowton manages to make a clearance.
The referee starts the match.
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