The identity of the author of Lazarillo has been a puzzle for nearly four hundred years. Given the subversive nature of Lazarillo and its open criticism of the Catholic Church, it is likely that the author chose to remain anonymous out of fear of religious persecution.
Neither the author nor the date and place of the first appearance of the work is known. It appeared anonymously; and no author's name was accredited to it until 1605, when the Hieronymite monk José de Sigüenza named as its author Fray Juan de Ortega. Two years later, it was accredited by the Belgian Valère André to Diego Hurtado de Mendoza. In 1608, André Schott repeated this assertion, although less categorically. Despite these claims, the assignment of the work to Diego Hurtado de Mendoza was generally accepted, until Alfred Paul Victor Morel-Fatio, in 1888, demonstrated the untenability of that candidate. The earliest known editions are the four of Alcalá de Henares, Antwerp, Medina del Campo, and Burgos, all of which appeared in 1554. Two continuations (or second parts) appeared – one, anonymously, in 1555, and the other, accredited to H. Luna, in 1620.
There has been some suggestion that the author was originally of Jewish extraction, who in 1492 had to convert to Catholicism to avoid being expelled from Spain; it could be used to explain the animosity towards the Catholic Church displayed in the book. Apart from the chronological difficulties this hypothesis presents, it should be noted that Catholic criticism of Catholic clergy, including the pope, was common; by then, such criticism had had a long and even reputable tradition that can be seen in the works of famous Catholic writers such as Chaucer, Dante and Erasmus.
Documents recently discovered by the Spanish paleographer Mercedes Agulló support the hypothesis that the author was, in fact, Diego Hurtado de Mendoza.