St Mirren came from behind to beat Hearts in one of the most dramatic finals witnessed at Hampden for many a year.
Ryan Stevenson opened the scoring for the Jambos with a drive in the 10th minute but in the 37th minute, against the run of play, Esmael Goncalves levelled from close range.
A minute into the second half veteran striker Steven Thompson converted a Paul Dummett cross before Conor Newton drove in number three.
Although Stevenson reduced the deficit with six minutes remaining to ensure a nervy ending, Danny Lennon's side held out.
It was an momentous Buddies victory that in truth looked unlikely for most of the first half as Hearts looked in complete control
However, that will not bother the thousands of Paisley Buddies who celebrated at the final whistle.
There was a massive Hearts support inside the national stadium but the smaller St Mirren contingent were just as noisy, creating a fabulous atmosphere at kick-off time.
St Mirren appeared to have survived some early pressure and as they worked their way into the game their first effort came in the eighth minute when a clever chip from Paul McGowan from the edge of the box sailed just past.
However, Hearts raced up the pitch moments later and scored.
Skipper Jim Goodwin's crunching tackle on Jambos striker Michael Ngoo saw the ball fall to Stevenson who faced up to Dummett outside the Buddies' box and he appeared to be the taking a little too much time to get his shot away.
There were five black and white jerseys around him when he eventually pulled the trigger and to the joy of the Jambos' supporters the ball nicked off Dummett before beating the flailing Samson.
The Paisley side looked gripped by nerves and unable to get any support to lone striker Thompson.
In the 20th minute the impressive Jamie Walker sent in a great cross from the left which took Samson out of the equation but Sutton was stretching and could only head the ball off the back post and behind.
The traffic remained mostly Paisley-bound.
In the 27th minute Samson had to react smartly to push away Kevin McHattie's in-swinging free-kick which evaded a clutch of players and almost sneaked in at the far post.
Then, Tynecastle midfielder Mehdi Taouil wriggled his way into the Saints box before sending a cross-cum-shot just past the far post, all of which meant Goncalves's equaliser in the 37th minute came as a surprise.
Thompson nipped in front of Gorgie stopper Danny Wilson sent Gary Teale racing down the right-wing with McHattie in his wake and when the former Derby winger cut the ball across goal the St Mirren forward, who had scored in the semi-final win over Celtic, stroked it into the empty net to change totally the complexion of the game.
As Hearts wobbled MacDonald had to race from his goal to thwart Teale as the Saints finished the half on top.
The second half was barely a minute old when Thompson fired St Mirren ahead.
Midfielder John McGinn fed Dummett on the left and when his cross came into the box the former Dundee United and Rangers striker beat Wilson to the ball before knocking it first-time past MacDonald.
Hearts were stunned but quickly responded. Walker fired a right-footed drive from 25 yards wide of the far post.
After good work by Taouil on the right-hand side, Samson had to make a point-blank save from Ngoo, who then headed McHattie's corner over the bar.
At the other end, as the game stretched, MacDonald blocked a close-range attempt by Thompson before midfielder Paul McGowan drove the rebound wide.
However, in the 66th minute Saints put one hand on the trophy when Newton played a one-two with Goncalves before breaking past the Hearts defence to power his shot past MacDonald.
It was a remarkable turnaround and it was Hearts' turn to look helpless.
Arvydas Novikovas replaced Walker, Jason Holt came on for Ngoo while Dale Carrick came on for Taouil.
Thompson made way for Sam Parkin and McGinn was replaced by Graham Carey, both substitutions eliciting a huge ovation from the St Mirren supporters.
Time was running out for Hearts but Samson made a good save from McHattie's drive with defender Marc McAusland making a great block to deny Ngoo from the rebound, before Stevenson clipped the bar from close range.
However, it was the former Ayr United player who gave the Edinburgh side a lifeline in the 84th minute when he took a Ngoo pass and screwed the ball past Samson and into the far corner.
As the tension became almost unbearable in the final moments Stevenson forced a save from Samson with an angled-drive before hitting the outside of the post from the rebound.
As Hearts pushed for extra time in the three minutes added, the St Mirren fans urged the final whistle to arrive and when it did, the roar reached all the way to Paisley.