Партия социалистов-революционеров
People's Socialist Revolutionary Party (; HASI) was a non-legal Basque political party, considered commonly to be the political branch of ETA. It always ran as part of the coalition of the Basque National Liberation Movement, Herri Batasuna, until its self-dissolution in the 1990s. The party's acronym "HASI" means "to begin" in Basque language.