Alaves will contest a Copa del Rey final for the first time in their history after Edgar Mendez's late goal secured a 1-0 aggregate over Celta Vigo on Wednesday to set up a showdown with Barcelona.
Mauricio Pellegrino's men claimed a commendable 0-0 draw in last week's first leg and were good value for victory at Mendizorroza, as second-half substitute Edgar secured a famous win in what was the club's biggest match since losing to Liverpool in the 2000-01 UEFA Cup final.
Victory was nothing more than their general play deserved, as they showed far more attacking intent than their visitors - though Iago Aspas remained a real nuisance to them and went close to breaking the deadlock on two separate occasions in the first half.
The home side's problem in the first period was their inability to turn control into efforts on goal, failing to register a single shot on target.
They were better after the break, though, testing Sergio Alvarez more regularly and spending almost the entire second period in the ascendancy.
And eventually the breakthrough came eight minutes from time, as Edgar scored a lovely solo goal to send Alaves through to an historic final.
Sensing the potential for history, there was a vibrant atmosphere in the stands throughout and that seemed to contribute to a positive start by the home side, as they pushed men forward and looked full of purpose.
But Celta crafted the match's first chance 12 minutes in, as Aspas flicked the ball through his marker's legs and sent a controlled effort towards the bottom-left corner from a tight angle, only to see a full-stretch Fernando Pacheco brilliantly tip it just wide of the post.
The visitors were also made to worry shortly after, with Ibai Gomez's 20-yard free-kick landing on the roof of the net.
Although Alaves exerted more control in midfield, Celta continued to look a threat on the break and a moment of Aspas brilliance just before the half-hour mark nearly gave them a crucial away goal.
The striker latched on to a misjudged header down the right flank and looped a half-volley over Pacheco and, unfortunately for Celta, on to the top of the goal.
Proceedings were rather less frantic at the start of the second period, though Alaves continued to look more committed to attacking and went close again after an hour - Deyverson seeing his 10-yard half-volley deflected over after the visitors failed to clear a corner.
But Celta's counter-attacking approach almost paid off a few moments later, as they caught Alaves short at the back and Daniel Wass inexplicably missed the target from six yards, though the offside flag saved him from some embarrassment.
Alaves were starting to up the ante, though, with Sergio Alvarez denying Ibai Gomez from distance, before Deyverson slammed an effort over from 25 yards when he appeared to have the time to get into the box.
Alvarez was ultimately rendered helpless in the 82nd minute, however, as Edgar - brought on for Gaizka Toquero just a few moments earlier - burst through the Celta defence and applied a clever finish beyond the goalkeeper to wrap up a huge win in fitting style.