[10] The major rivalry is between Athletic Bilbao and Real Sociedad, representing their home provinces of Biscay and Gipuzkoa, known as 'the' Basque derby, which has been played over 140 times in the league alone.

[17] The third club, Deportivo Alavés, has not won any major honours, coming closest by finishing runners-up in the 2000–01 UEFA Cup[18][19] and the 2016–17 Copa del Rey.

A dramatic match between Alavés and Real Sociedad took place in June 2008 at Mendizorrotza, with both clubs involved in battles at either end of the second division table going into the penultimate round.

A smaller organisation historically than Álaves reflected in fanbase and stadium, their home town of Eibar has a population of under 30,000 and is located midway between Bilbao and San Sebastián with many of the residents supporting either Athletic or Real Sociedad.

[39] While they were minnows in La Liga, Eibar have been very much at the head of the food chain of small-town Basque football since the 1980s and have habitually competed at a higher level than their geographical neighbours from the territory's numerous inland mountain valley communities (Elgoibar, Lagun Onak, Amorebieta, Beasain, Durango, Tolosa, Mondragón, Bergara, Gernika, Anaitasuna and Aretxabaleta).

The regional dimension is also present when Athletic Bilbao meet the biggest club in the Cantabria region, Racing de Santander, but that historic[48][49][50] and unpredictable[51] rivalry, which has been referred to in the past as 'the duel of the North'[52] is dormant as Racing have not played in the top tier since 2012;[53][54] a cup tie in 2016 resulted in a straightforward Athletic win[55] but fans of both teams were reminded of a previous meeting in 2008 when the opposite outcome occurred.

Due to this strong performance, both were invited to participate in the inaugural season of La Liga in 1929, Real Unión surviving for the first four years of the competition and Arenas for seven.

On the other hand, participation at a higher level increased: three Basque teams would be involved in 2021–22 Segunda División (from there being none the previous season) as Eibar's relegation coincided with the promotion of Amorebieta (for the first time ever)[61] and Real Sociedad B, after an absence of 59 years.

They are one of a number of teams from the settlements lining either bank of the Estuary of Bilbao north of the city proper, along with Arenas and others including Erandio (who also faded from a greater prominence in the game's early decades), Portugalete, Sestao, Santurtzi and Leioa.

The canteras (youth academies) of Athletic Bilbao and Real Sociedad have been analysed as being among the most productive in Europe,[63][64][65] with the vast majority of the players originating from the Basque region (population approximately three million).

in the modern era, no player has appeared for the first team of all four clubs in the league, although several have featured for three, including José Félix Guerrero, Xabier Castillo, Gaizka Toquero, Gaizka Garitano, Yuri Berchiche, Borja Viguera, Jon Moya, Joseba Arriaga, Luis Prieto, Edu Alonso, Luciano Iturrino, Ricardo Arrien, Xabier Guruzeta, Elías Querejeta, César and Josu Sarriegi.

[69] In 2019, Garitano (now head coach of Athletic) faced up to Eibar with three former Armeros players, all signed the previous summer, in his team: Berchiche, Dani García and Ander Capa.

[99][83] In 2020, Osasuna received two payments relating to Athletic players: approximately €150,000 in development fees came from sporting milestones achieved by Oihan Sancet who moved to Bilbao in 2015 as a juvenile under freedom of contract, and €1.5 million from Torino who sold Álex Berenguer to Athletic whilst a clause was in his contract triggering an additional payment[100] – specifically designed to hinder a move to the Pamplona club's rivals and agreed in the wake of the Areso dispute.

[101] In a rare move in the opposite direction, Areso was welcomed back to Osasuna in the summer of 2021, still looked upon as a good prospect but never used by Athletic's first team and also frozen out in the reserve squad after he and the club failed to agree contractual terms.

[109] In the first edition of the Euskal Herriko Futbol Txapelketa (Basque Country Football Championship), the participants were Athletic Bilbao and Alavés;[110] in a somewhat embarrassing outcome, the match in Barakaldo was abandoned by the referee in the closing minutes due to disorder among the players with the score at 2–2, and no winner was declared.