For Barca, it could act as step two on their way to the treble, while Bilbao will be looking to spoil the party in the Catalans' own back yard.
The odds are stacked against Bilbao going into this weekend's match. Not only do they face the might of Barcelona, but the final just happens to be at Camp Nou, where they have not won a match since 2001.
That won't be the only long-standing drought they will need to break if they are to lift the trophy on Saturday, however.
Bilbao have not won the Copa del Rey since their memorable 1983-84 season, when they beat none other than Barcelona in the final to clinch the league and cup double.
That is too long without success in a competition that is inextricably linked with the Basque outfit, who have won it 23 times. Only Barcelona (26) have lifted the trophy more often.
With just a solitary Europa League title to their name since then, the thirst for silverware is growing ever greater for Bilbao, but the 39-point gap between these two teams in the final La Liga standings demonstrates just how tough an ask it will be for Ernesto Valverde's men.
Bilbao ended up seventh in the table, five points adrift of the final Europa League spot, but they had a strong end to the campaign. They were unbeaten in their final seven matches of the season and have lost just four of their last 20 games in all competitions, including an impressive 4-0 triumph over Villarreal on the final day.
Their passage through to this final has not exactly been smooth, though, winning just half of their eight outings. Alcoyana, Celta Vigo, Malaga and Espanyol have all been dispatched on aggregate along the way, however, while Bilbao remain unbeaten on the road in this season's competition.
Indeed, they won in Barcelona in the second leg of their semi-final, beating Espanyol 2-0 to clinch a 3-1 aggregate triumph that saw them through to a third final in the last six years.
Bilbao were almost denied that opportunity by the threat of a strike in Spanish football over TV rights, but that has now been resolved and the Basque side will look to upset the odds this weekend.
Recent form in Copa del Rey: WLDWDW
Recent form (all competitions): WDDDWW
One down, two to go. Barcelona officially lifted the La Liga trophy last weekend to complete the first part of a prospective treble, with the Champions League final to come a week on Saturday.
It has been a scintillating season for the Catalan giants, and it would take a brave person to bet against them repeating the same three-trophy haul that Pep Guardiola's side memorably clinched in 2008-09.
That side is regarded by some to be the best club team of all time, but Luis Enrique's current crop of players look to be on course to challenge them.
The front three of Lionel Messi, Luis Suarez and Neymar took their combined tally for the season to a staggering 117 in the final league match of the campaign, and it would be a surprise if they weren't to further extend that record in the remaining two matches.
Neymar alone has six goals in five Copa del Rey appearances this season, including two in the 6-2 aggregate semi-final victory over Villarreal that saw them reach a second consecutive final. In all, Barcelona have won this competition a record 26 times, although only two of those have come in the last 17 years. Both of their most recent triumphs came against Bilbao, though.
The Blaugrana ended the league campaign two points clear of runners-up Real Madrid, although they did blow a two-goal advantage against Deportivo on the final day - a result that saw the visitors to Camp Nou dramatically stay up.
That ended a six-match domestic winning streak in which they had not conceded a single goal, while they have not been beaten on Spanish soil since February. That loss did come at home, but their overall record in front of their own fans this season is remarkable - 26 victories, one draw and just two defeats from their 29 outings.
What's more, they have conceded just 15 goals in that time, demonstrating the improvement the team has made at the back as well as up front. They have scored 31 times in their eight Copa del Rey ties this season, all of which have ended in victories.
More than just another trophy for their cabinet rests on them making it nine on the bounce this weekend, as they look to set up a treble showdown with fellow domestic league and cup champions Juventus on June 6.
Recent form in Copa del Rey: WWWWWW
Recent form (all competitions): WWWLWD
Barcelona's biggest concern comes with Suarez, who has returned to training for the club but remains a substantial doubt for this weekend.
Should he fail to recover, Pedro, who himself has five goals in five Copa del Rey games this season, is expected to join Messi and Neymar in the frontline.
Enrique has no other injury concerns, with Thomas Vermaelen coming through his long-awaited debut unscathed at the weekend, but the Barcelona boss does have one or two decisions to make.
Stalwart Xavi made his final league appearance for the club on Saturday and will be desperate to turn out one last time at Camp Nou in his penultimate Barcelona match, but he is likely to have to settle for a place on the bench.
Aritz Aduriz, whose brace on the final day made it 10 goals in his last 11 games and 26 for the season, will continue to lead the line for the underdogs.
Athletic Bilbao possible starting lineup:
Herrerin; Iraola, Etxeita, Laporte, Balenziaga; Benat, San Jose, Rico, Aketxe, Williams; Aduriz
Barcelona possible starting lineup:
Ter Stegen; Alves, Pique, Mascherano, Alba; Iniesta, Busquets, Rakitic; Messi, Suarez, Neymar
Head To Head
These two sides have met in the final of this competition seven times before, with Barcelona winning five of those and Bilbao two. The most recent two finals, in 2009 and 2012, have both gone the way of Barca.
The Catalans have the upper hand when it comes to recent history in all competitions too, with Bilbao only winning one of the last 24 meetings between these two sides.
That includes two Barca victories in La Liga this season, with Neymar scoring both goals in a 2-0 win at Camp Nou in September before adding another to help Enrique's side to a 5-2 triumph in February.
We say: Athletic Bilbao 0-3 Barcelona
Bilbao have a long and storied history in this competition, but in the modern day there are few teams who can compete with this Barcelona side. They have a defence that can keep sides out and arguably the most potent attacking trio ever assembled at the other end. Being at home will only help Barca, and they will be desperate not to blow the chance of a treble in what is, on paper at least, the easiest strand of it. We are going for a comfortable 'home' win and a treble showdown against Juventus.