This article is a study of the national holiday of 12 October, one of the most long-lasting symbolic components of Spanish nationalism. Transnational in nature, this celebration of Spain’s existence constitutes an exception among similar national holidays, in that it is based upon the country’s role in the Americas and nostalgia for empire as founding elements of national identity. By analysing the changing celebration of this anniversary along the twentieth century, in rituals and language, the article highlights both the different imaginaries evoked and the roles played by particular actors and institutions in different stages of the construction of the national state, including its regional and local identities. Our analysis of the progress of this celebration, from its inception in the late nineteenth century to the present day, as first Fiesta de la Raza, then Día de la Hispanidad and now just ‘National Day’, suggests that its durability, maintained for nearly a century, stems from the notably ductile nature of the myths associated with it. Adaptable to regimes and political challenges of varied kinds, this commemoration melds together the inheritance of liberalism, the national-Catholic tradition and ‘regionalized nationalism’, all of which have been key elements in Spanish political history in the twentieth century.