Real Sociedad ended the Copa del Rey hopes of second division Mirandes on Wednesday with a 1-0 win which moved them into the final for the first time in 32 years.
Sociedad had already won the first leg 2-1 and cemented their spot in the decider when striker Mikel Oyarzabal scored a 41st-minute penalty after a handball in the area by a Mirandes player.
The April 18 final in Seville could be an all-Basque affair with Athletic Bilbao defending a 1-0 lead against fellow La Liga mid-table side Granada in their semi-final second leg on Thursday.
Mirandes were attempting to become the first-second division club to reach the final since 1980.
Real Sociedad, who were Copa del Rey winners in 1909 and 1987 and knocked out Real Madrid 4-3 in this season’s quarter-finals, will be playing in their first final since 1988 when they lost 1-0 to Barcelona.
With 23 titles, Athletic Bilbao are second on the all-time list of Cup winners behind Barcelona who have triumphed 30 times.