Basque nationalism is a form of nationalism that asserts that Basques are a nation and promotes the political unity of the Basques. Since its inception in the late 19th century, Basque nationalism has included separatist movements.
Basque nationalism, spanning three different regions in two states (the Basque Autonomous Community and Navarre in Spain, and the French Basque Country in France) is "irredentist in nature" as it favors political unification of all the Basque-speaking provinces.
Basque nationalism is rooted in Carlism and the loss, by the laws of 1839 and 1876, of the Ancien Régime relationship between the Spanish Basque provinces and the crown of Spain. During this time, the reactionary Fuerista movement pleaded for the maintenance of the fueros system and territorial autonomy against the centralizing pressures from liberal or conservative governments in Madrid. The Spanish government suppressed the fueros after the Third Carlist War.
The fueros were the native decision making and justice system issued from consuetudinary law prevailing in the Basque territories and Pyrenees. They are first recorded in the Kingdom of Navarre, confirming its charter system also across the western Basque territories during the High Middle Ages. In the wake of Castile's conquest of Gipuzkoa, Álava and Durango (1200), the fueros were partially ratified by the kings of Castile and acted as part of the Basque legal system dealing with matters regarding the political ties of the Basque districts with the crown. The Fueros guaranteed the Basques a separate position in Spain with their own tax and political status. While its corpus is extensive, prerogatives contained in them set out for one that Basques were not subject to direct levee to the Castilian army, although many volunteered.