Atletico Madrid struggled through a 3-0 Copa del Rey semifinal second leg defeat at Barcelona on Tuesday but scraped into the final 4-3 on aggregate.
The Spanish champions almost produced a comeback for the ages after their 4-0 first leg defeat in early February, but fell just short at Camp Nou.
Youngster Marc Bernal netted twice for the record 32-time winners and Raphinha scored a penalty as Barcelona tried in vain to claw back Diego Simeone's side's lead.
Atletico, who clung on desperately in the final stages, returned to the final for the first time since 2013.
They will face Real Sociedad or Athletic Bilbao, who meet Wednesday, in the second semifinal second leg.
Barcelona came out flying and Fermin Lopez's long-range effort just over the bar set the tone, as Hansi Flick's side threw everything they had at a potential comeback.
They were dealt an early setback when Jules Kounde went off injured in the opening stages. Antoine Griezmann came close against his former side as Atletico threatened on the counter-attack.
Ferran Torres fired wide and had a shot saved low at the near post by Atletico goalkeeper Juan Musso before Barcelona took the lead.
Teenage star Lamine Yamal drilled across the face of goal for Bernal to finish from close range, with one 18-year-old setting up another.
Ademola Lookman headed narrowly off-target for Atletico and came to rue the miss as Barca doubled their advantage before the interval.
Spain midfielder Pedri was tripped in the box by Marc Pubill and Raphinha sent Musso the wrong way from the spot.
Joao Cancelo almost grabbed the third but his shot was beaten away by Musso at full stretch, with Diego Simeone's team on the ropes.
Bernal set up a frantic finale when he volleyed home Cancelo's swirling cross to take Barca within one goal of the crumbling Rojiblancos.
Flick put centre-back Ronald Araujo up front for the final stages, in search of a fourth goal to "make the impossible possible", as he called on his team to do before the game.
Gerard Martin hammered narrowly over the bar as Barca turned the screw, with fans roaring the team on through six minutes of stoppage time.
The Rojiblancos fended off Barca and booked their place in the Seville final on April 18.