The visitors were bracing themselves for humiliation when two down and a man worse off following the captain's moment of madness but Torres came good at the death to triumph
The Blues won the semifinal matchup with a 3-2 aggregate scoreline.
An astonishing end to the first half saw Sergio Busquets open the scoring from close range before John Terry saw red for kneeing Alexis Sanchez in the back off the ball.
Andres Iniesta had then calmly finished from a Lionel Messi through-ball to seemingly put the hosts clear before Ramires' incredible chipped goal on the counterattack.
Didier Drogba gave away a penalty at the start of the second half but Messi uncharacteristically cracked it against the crossbar, and it fell to substitute Torres in added time to put it out of the hosts' reach after rounding Victor Valdes.
Pep Guardiola surprised some by benching Dani Alves, opting for three at the back with Gerard Pique recalled. Youngster Isaac Cuenca was also drafted in to the forward four.
Roberto Di Matteo, meanwhile, selected the same side that beat Barca 1-0 at Stamford Bridge, with Drogba leading the line once again.
Barcelona started ominously. Messi and Alexis exchanged a quickfire interchange of several short passes to smuggle the Argentine through into the area, but his effort flew into the side netting.
Chelsea was worried within six minutes when Gary Cahill slipped in the box, clutching his hamstring, and though the center back briefly tried to carry on, Jose Bosingwa replaced him.
Pique was then in the wars, colliding with his own goalkeeper and requiring medical treatment after landing on his head, but he was able to get back up again.
After an opening 19 minutes dominated more by injuries than chances, goalkeeper Petr Cech was called into action. More scintillating close passes on the edge of the box again put Messi through, this time centrally, but his finish lacked any venom and Cech kept it out with his foot.
Drogba started causing some problems thereafter, hooking a ball over from the corner of the area before bypassing Pique a moment later, though his angle was too tight to shoot on target.
That signaled Pique’s last contribution as he succumbed to his earlier knock and Alves returned in his place, Barca maintaining its three-man back line with the Brazilian on the right of it.
After several minutes of frustration the hosts broke through. As Chelsea failed to clear a corner, Cuenca picked the ball up on the left and, with Terry playing several men onside, Busquets was on hand to turn in a simple finish.
Terry's evening got a lot worse, though, as moments after the goal, while standing off the ball alongside Alexis, he appeared to knee the Chilean in the back. The referee, Cuneyt Cakir, produced the red card after prompting from his assistant.
Chelsea’s despair was compounded just before halftime. Iniesta infiltrated forward outside the last defender to receive Messi’s through-ball and dispatched an expert finish calmly past Cech.
But out of nowhere, the visitors got back in it. Ramires, who was booked in the aftermath of Iniesta’s goal and would play no part in the final, latched on to Frank Lampard’s pass on the end of a powerful run, and the Brazilian delivered a thrilling chip over Victor Valdes to rekindle the Blues’ hopes.
The second half started disastrously, though. Drogba, back to help his depleted side out, mistimed his tackle on Fabregas, gifting Barca a penalty. Messi stepped up, ready for his first goal against Chelsea - but crashed his effort onto the crossbar.
Alexis should have done better on 54 minutes when his header, from a right-flank cross, dropped weakly to the left of Cech's far post.
Drogba raised eyebrows a moment later when he beat two men in his own half - including the advanced Carles Puyol - and attempted a drive from the halfway line, though Valdes' save made it look more dangerous than it was.
There might have been a game-deciding second for Chelsea in the 67th minute as substitute Salomon Kalou battled forward on his own, getting past his markers before coming over as a rabbit in the headlights at the crucial moment, allowing Valdes to scoop up.
As the bookings mounted up - Lampard, Messi and Ivanovic, the latter missing the final - Barcelona's chances dried up. Busquets, going for an unlikely double, was only able to scoop awkwardly over as the final phase beckoned.
The home fans cheered when Alexis had the ball in the net on 81 minutes but substitute Fernando Torres was spared blame for losing his man as it was ruled out for an offside in the build-up.
Just moments later, too, Messi came achingly close, firing against the post from a snapshot as Chelsea held on for dear life, Cech's touch key in drifting it onto the woodwork.
As Barca threw its last at Chelsea, it was undone. With nobody in Barca's own half, Torres suddenly found himself clean through with space to burn. Racing forward and rounding Valdes with his most composed head on, the Spaniard rolled it into an empty net to seal a famous triumph for Di Matteo's men.