A stoppage time strike from Australian international Tom Rogic saw Celtic come from behind to defeat Aberdeen 2-1 to lift the Scottish Cup and seal a historic domestic treble the hard way.
Aberdeen pushed Celtic all the way as history made
Jonny Hayes gave Aberdeen a ninth minute lead which was quickly cancelled out by Celtic's Stuart Armstrong two minutes later. The game looked destined for extra time before substitute Rogic scored a superb solo goal in the second minute of added on time to break the Dons' supporters hearts and ensure Celtic won the Scottish Cup for a record-extending 37th time.
The Hoops are now the first Scottish team to end a season unbeaten domestically as Brendan Rodgers joins Jock Stein and Martin O'Neill as the only Celtic managers to lead the Glasgow giants to all three major honours in the same season.
"It is a monumental achievement," the Celtic manager said of his side's first treble since 2001. "It was a very tough game and obviously to win it as we did was special. It's an incredible feeling and congratulations to the players."
Painful ending for Aberdeen
"I think that any time you lose a game in injury time is difficult but it's compounded by it being a cup final," McInnes said.
"There was nothing in the game except we lacked a wee bit of legs and impetus to go forward and apply pressure."
After basking in glorious sunshine for the previous week, a torrential downpour welcomed the players out on to the pitch at Hampden as they observed a minute's silence for the victims of the terrorist attack in Manchester earlier this week.
Good start for the Dons
The conditions didn't seem to bother the fired up Aberdeen players as their high-tempo start paid off when Hayes fired them into the lead. Leigh Griffiths switched off at a Niall McGinn corner allowing the Irishman space to send a low volley into the net despite the best efforts of Kieran Tierney on the line.
Aberdeen's lead lasted just two minutes as Armstrong hauled Celtic level. Callum McGregor danced past a couple of tackles before slipping the ball across the edge of the box to Armstrong, who lashed a low shot between a couple of Dons defenders and into the bottom right-hand corner.
Celtic's joy was short-lived as left-back Tierney was forced off with a mouth injury after being caught in the face by Jayden Stockley's swinging arm. The introduction of Socceroo star Rogic saw Celtic switch to a back three with Niall McGinn, Ryan Jack and Stockley forcing Craig Gordon into saves as the Hoops struggled to adjust to the change.
Chances galore as Celtic and Aberdeen push for win
A reorganised Celtic emerged after the break and immediately came close when Griffiths got behind the Dons defence only to see his deflected shot bounce narrowly wide. Sinclair then beat the offside trap to collect a lofted pass from Rogic but Joe Lewis was off his line quickly to block his shot.
However, it was the Dons who should have found themselves in front again. Hayes robbed McGregor of possession just inside the Celtic half and ran at goal but his pass across the box was behind Kenny McLean and a glorious chance was spurned.
Patrick Roberts, who missed the U20 World Cup with England to play in the final, then looked to inspire the Hoops as he twisted and turned on the edge of the box before firing a shot that cannoned off the base of the post. Player of the year Sinclair then fluffed a chance to win as he completely miss-hit his volley from a Griffiths pass allowing Lewis to make the save.
It didn't matter though, as Rogic glided past two Dons defenders before rifling an angled shot low under Lewis to beat the 'keeper and seal victory in the week that the Hoops celebrated the 50th anniversary of their European Cup win.