Barcelona is one of three founding members of the Primera División that have never been relegated from the top division, along with Athletic Bilbao and Real Madrid. In 2009, Barcelona became the first Spanish club to win the continental treble consisting of La Liga, Copa del Rey, and the UEFA Champions League, and also became the first football club to win six out of six competitions in a single year, completing the sextuple in also winning the Spanish Super Cup, UEFA Super Cup and FIFA Club World Cup. In 2011, the club became European champions again and won five trophies. This Barcelona team, which reached a record six consecutive Champions League semi-finals and won 14 trophies in just four years under Pep Guardiola, is considered by some in the sport to be the greatest team of all time. In June 2015, Barcelona became the first European club in history to achieve the continental treble twice.

Besides Barcelona and Real Madrid, what other team has remained in the Primera Division?