Madrid - Stephane Mbia headed home in the fifth minute of stoppage time to take Sevilla into the Europa League final on away goals despite losing 3-1 on the night away to Valencia.
An early strike from Sofiane Feghouli and Beto's own goal had wiped out Sevilla's 2-0 first leg advantage inside 25 minutes.
Jeremy Mathieu's goal midway through the second-half then seemed to have Valencia on route to the final, but Mbia powered home Federico Fazio's flick-on from a long throw to deny Los Che with the last attack of the game.
"I think it is the happiest moment of my life," said Mbia, who is on-loan at the Andalusian club from Queens Park Rangers.
"It is unbelievable. I don't have the words to describe it."
Inspired by overcoming a 3-0 first leg defeat to beat Basel 5-0 at home in the return in the quarter-finals, Valencia went ahead on 14 minutes when Feghouli cut inside onto his left foot and his shot deflected off Fazio and flew into the roof of the net.
The Algerian international came close again when he was denied by a fine low save by Beto.
However, the Portuguese goalkeeper was unfortunate moments later when the ball rebounded in off his back after he had made a fine save to turn Jonas Goncalves' header onto the bar.
Valencia goalkeeper Diego Alves was then called into action to prevent Sevilla registering a crucial away goal as he brilliantly smothered Jose Antonio Reyes' effort from point-blank range.
The hosts looked to have sealed their place in the final 21 minutes from time when Mathieu thrashed home after the ball fell perfectly for the French defender from Fede's corner.
However, Mbia's dramatic intervention means it will instead be two-time winners Sevilla who will face Benfica in the final in Turin on May 16.