Match ends, St Johnstone 2, Aberdeen 1.
St Johnstone reached their first Scottish Cup final in the club's 130-year history after a second-half fightback against Aberdeen.
Two goals from Stevie May sent the Perth club into the 17 May showpiece against Dundee United.
Aberdeen had taken the lead through Niall McGinn and looked the more dominant side in the opening period.
Saints changed their shape at half-time, and May's two goals were their reward for renewed vigour and intent.
The result came as a surprise, given Aberdeen carried the greater weight of expectation into the game.
It had already been a season of triumphant progress, since they won the League Cup final and are challenging strongly to finish second in the Premiership, while St Johnstone had not even managed to score in four games against Derek McInnes's side this season.
Aberdeen brought a larger support to Ibrox, too, as they emphasised the notion of being a revived force in Scottish football.
Caution initially prevailed, though, in a tentative opening. St Johnstone might have felt restrained by the memory of the League Cup semi-final, in which they conceded early against Aberdeen and lost another three goals as they chased the game.
The careful approach was still undone, though, because Aberdeen opened the scoring when Peter Pawlett slipped a pass through the St Johnstone defence for McGinn. The forward showed composure and nous to clip a shot beyond the reach of the goalkeeper Alan Mannus.
A surge of confidence swept through Aberdeen and they ought to have scored a second when McGinn broke up the right wing and curled a cross-field pass into the path of Adam Rooney, but Mannus raced from his goal and blocked the striker's effort.
St Johnstone lacked dynamism in midfield, leaving Steven MacLean isolated when he received the ball at centre-forward, with May trying to play ahead of him.
Aberdeen's front four were sharper and slicker in their movement and interchanges, but May forced Jamie Langfield into a sharp close-range stop in Saints' only real opening of the first half.
The half-time interval allowed for a period of critical reflection, and the St Johnstone manager Tommy Wright changed the shape of his team to 4-3-3, with May moving to the left flank and David Wotherspoon into a more central role.
The benefit was immediate, as Saints played with much greater attacking aggression, and forced Aberdeen into a period of anxiety.
Even from a withdrawn and wider role, May was still a key influence. He is a powerful and direct runner, but it was his resourcefulness that proved telling. When the ball broke to the burly striker inside the penalty area, he took a touch, spun round and stabbed a shot beyond Langfield from close range.
Pawlett should have done better than slice a shot out for a throw-in, Barry Robson headed straight into Mannus's arms, and McGinn nodded wide from seven yards when free at the back post. But these were merely interruptions to St Johnstone's command of the second period.
Even as the game moved into the final 10 minutes, when nerves can inhibit players, St Johnstone remained committed in attack, and the excellent MacLean ran in behind the Aberdeen defence to gather the ball before laying it back to May.
The striker took a touch before surging into the area then prodding the ball beneath Langfield.
- 17MayBooked at 85mins
- 29O'HalloranSubstituted forCreggat 89'minutes
- 5ConsidineSubstituted forVernonat 90'minutes
- William Collum
- Shots on Target
Second Half ends, St Johnstone 2, Aberdeen 1.
Chris Millar (St Johnstone) wins a free kick in the defensive half.
Foul by Scott Vernon (Aberdeen).
Substitution, Aberdeen. Scott Vernon replaces Andrew Considine.
Substitution, St Johnstone. Patrick Cregg replaces Michael O'Halloran.
Steve May (St Johnstone) is shown the yellow card.
Goal! St Johnstone 2, Aberdeen 1. Steve May (St Johnstone) right footed shot from the centre of the box to the bottom left corner. Assisted by Steven MacLean.
Brian Easton (St Johnstone) wins a free kick on the right wing.
Foul by Shaleum Logan (Aberdeen).
Foul by Steven MacLean (St Johnstone).
Mark Reynolds (Aberdeen) wins a free kick in the attacking half.
Foul by Steven MacLean (St Johnstone).
Russell Anderson (Aberdeen) wins a free kick in the defensive half.
Attempt missed. Steve May (St Johnstone) right footed shot from outside the box is high and wide to the right.
Chris Millar (St Johnstone) wins a free kick in the attacking half.
Foul by Adam Rooney (Aberdeen).
Attempt missed. Niall McGinn (Aberdeen) header from the centre of the box is close, but misses to the left.
Steve May (St Johnstone) wins a free kick on the right wing.
Foul by Barry Robson (Aberdeen).