The club is one of three founding members of the "Primera División" that have never been relegated from the top division since its inception in 1929, the others being Real Madrid and Barcelona. These three clubs, along with Osasuna, are the only four professional clubs in Spain that are not sports corporations; instead they are owned and operated by club members. Athletic's main rivals are Real Sociedad, against whom it contests the Basque derby, and Real Madrid, due to sporting and political rivalry. At various points in the club's history, further Basque league derbies have been contested against Alavés, Eibar and Osasuna.