Athletic Club Bilbao

Athletic Club Bilbao has never been relegated from La Liga, a 94-year streak unmatched by any other Spanish club. Their Basque-only transfer policy, unique among top-flight teams, produced a 2023-24 average squad age of 24.5 years—3.2 years younger than the average La Liga squad. The 53,289-seat San Mamés, known as 'La Catedral,' saw 88% capacity utilization last season. Athletic's 8 Copa del Rey titles are fewer than Real Madrid's 20, but their 24 consecutive top-10 finishes since 2000 highlight enduring consistency.