Athletic Bilbao made it three finals in a year as they saw off Levante 2-1 in extra time on the night and 3-2 on aggregate to set up a Copa del Rey showdown with Barcelona.
Supercopa de Espana champions Athletic reached last season's Copa final but, due to the impact of the coronavirus pandemic, they are yet to play it – the match against their rivals Real Sociedad is set for April 3.
In a bizarre turn of events, Athletic will be playing both finals in the space of two weeks, with Alex Berenguer's deflected, extra-time winner sealing their progress and seeing them equal Real Madrid on 39 appearances in Copa del Rey finals.
It completed a turnaround for the 23-time Copa winners, with Raul Garcia's penalty having cancelled out Roger Marti's opener.
Athletic started brightly, yet it was the hosts who struck first – Marti sweeping a neat, on-the-spin finish beyond Unai Simon.
Iker Muniain should have hit back seven minutes later only to head wide from Oscar de Marcos' precise cross.
Athletic had their equaliser, and a vital away goal, on the half-hour, though, with Raul Garcia slamming in from the spot after he had been felled by Oscar Duarte.
Jorge de Frutos prodded wide from a decent chance to restore Levante's lead before Yeray Alvarez turned Jorge Miramon's cross against the foot of Athletic's post.
Raul Garcia turned provider 20 minutes after the restart, presenting Inaki Williams with his first opening, only for Athletic's forward to slice his effort.
Muniain slipped at a crucial moment after wriggling his way to the six-yard box before Berenguer's improvised header looped wide.
Levante went closest in the first half of extra-time – Simon sensationally keeping out Enis Bardhi's free-kick.
Yet it was Athletic who finally settled the contest. Berenguer tried his luck from range, his effort taking a huge deflection off Nikola Vukcevic and clipping in off the woodwork to send the visitors through.
What does it mean? Two finals in fourteen days for Athletic
Both Athletic and La Real wanted last season's final to be postponed further in the hope of fans being able to attend a historic all-Basque showdown, with under a month left to go until that match takes place.
While it remains to be seen whether spectators will indeed be able to attend, Athletic – who defeated Barca in the Supercopa final earlier this year – now face the remarkable prospect of playing the finals of consecutive Copa del Rey campaigns in the space of just fourteen days; the first time that has happened.
Berenguer gets the rub of the green
Having gone close with a superb header when facing away from goal midway through the second half, Berenguer decided to take matters into his own hands in extra-time.
Athletic had been guilty of overplaying at times, but his long-range effort – his second attempt of the game – was on target and the diversion off the unfortunate Vukcevic gave Aitor Fernandez no chance.
Will Levante ever break their duck?
Founded 112 years ago, Levante are yet to reach the final of a cup competition. They had the chance to finally end their wait on Thursday.
The hosts did their all, mustering 10 attempts – four of which were on target – and going toe-to-toe with Athletic for possession (46.9 per cent compared to the visitors' 53.1). Ultimately, though, they fell short once more, and the Valencian club may well wonder if their fortunes are ever going to change.
Athletic's Basque rivals La Real are up next for Levante in LaLiga on Sunday, while Marcelino's team face Granada.