Basque Nationalist Action is a Basque nationalist party based in Spain. Founded in 1930, it was the first Basque nationalist political party to exist running on a socialist program. On 16 September 2008, the party was outlawed by the Spanish Supreme Court based on ties with ETA. The Spanish ruling was appealed to the European Court of Human Rights, which, after reviewing the question, upheld the Spanish courts on the matter.

Basque nationalism is a form of nationalism that asserts that Basques, an ethnic group indigenous to the western Pyrenees, are a nation and promotes the political unity of the Basques, today scattered between Spain and France. Since its inception in the late 19th century, Basque nationalism has included Basque independence movements.