The life of Pascual de Gayangos has been retold many times, and yet it is only now that we begin to grasp more comprehensively his personality and achievements. To date, the most extensive biography of Gayangos is the unfinished study by his disciple Pedro Roca published in a series of articles between 1897 and 1899. Although a number of works and a substantial number of Gayangos's letters have been published since then, Gayangos's definitive biography remains to be written. Such an account would result in a lengthy monograph if it encompassed a compre hensive picture of his life, scholarly production and achievements within the social, intellectual and political environment in which he was immersed, as well as a study of his contribution to the transmission of knowledge and the development of certain scholarly disciplines. Furthermore, no scholar easily resists the temptation to include fragments of letters from and to Gayangos – a tantalising ingredient which leaves nobody indifferent and which, as Sánchez Mariana has pointed out, is a rich source for the study of daily life and culture in nineteenth-century Spain, the circulation of books, and the reconstruction of private libraries. Having said this, my purpose here is to present a general overview of his biographical trajectory as a context for a broader analysis of some aspects of his personality, activities and historical background which will be dealt with in other chapters of this book. While trying to keep to a chronological narrative, it is also my intention to reconsider some question - able but deep-rooted ideas about Gayangos in light of recently unearthed sources.