Alessandro Murgia came off the bench to snatch Supercoppa Italiana glory as Lazio secured a breathless 3-2 win over Juventus amid remarkable late drama at Stadio Olimpico.
The hosts, playing in the showpiece by virtue of their 2-0 loss to Juve in May's Coppa Italia final, appeared to be cruising to victory by the same margin thanks to a double from Ciro Immobile.
The one-time Juventus youngster built upon 23 Serie A goals in his maiden season at Lazio by winning and converting a first-half penalty and expertly dispatching a header nine minutes after the interval.
Juventus offered little sign of mustering a response until Paulo Dybala scored a magnificent free-kick in the 85th minute and the Argentina forward converted from 12 yards in stoppage-time after Adam Marusic felled Alex Sandro.
But two other Lazio substitutes would give far more impressive accounts of themselves as Jordan Lukaku stormed down the left flank and allowed Murgia to add a final twist, condemning Juve to a third Supercoppa reverse in the past four seasons.
Juventus laid siege to the Lazio area during the early stages, Thomas Strakosha keeping out Juan Cuadrado's close-range attempt with his legs when he should have had no chance to prevent a goal from Alex Sandro's cutback.
It proved an eventful opening for the Albania goalkeeper, who got down sharply to deny Dybala and Gonzalo Higuain, and Lazio rewarded him by gaining a foothold in the contest.
Giorgio Chiellini, playing without his old ally Leonardo Bonucci in the Juventus defence, made a brilliant last-ditch tackle to thwart Immobile but the same player sprung the Serie A champion's backline in the 31st minute and was brought down by Gianluigi Buffon.
The booked veteran goalkeeper guessed correctly but could not get close to Immobile's well-struck effort.
Buffon was soon back in the action as Dusan Basta drilled an effort at him from Sergej Milinkovic-Savic's clever flick before Lucas Leiva sought a rare goal with a fierce long-ranger that was tipped over the bar.
Cuadrado, who was on the receiving end of a robust tackle from Lucas before half-time, saw a shot blocked shortly after the restart but Lazio doubled their lead in the 54th minute.
The Juve backline had lost its shape by the time Marco Parolo floated a cross to the far post and Immobile headed back across Buffon and in.
Immobile might have claimed the match ball when Senad Lulic played him through with an hour played but Buffon sprawled effectively at the forward's feet.
Miralem Pjanic's radar was unusually awry from a promising free-kick situation and Higuain prodded wide from substitute Douglas Costa's cross as the game entered its final quarter.
Buffon had to turn away a stinging Luis Alberto attempt before Dybala showed Pjanic how it was done from 25 yards.
The 23-year-old's viciously swerving strike shattered Lazio's previous calm and Marusic's foul on Alex Sandro was clumsy in the extreme as Dybala converted easily to have seemingly forced extra-time.
Sensing their moment slipping by, the hosts released Lukaku to storm down the left flank. Mattia De Sciglio's desperate slide tackle could not contain the Belgian and Murgia steered unerringly past Buffon to spark wild celebrations.