This thesis examines the concept of self-fashioning in the Spanish texts La Celestina and Farsa de Costança. Greenblatt's theory of self-fashioning in English Renaissance literature can also be applied to the analysis of these Medieval and Renaissance works of the Iberian Peninsula. Self-fashioning is a literary technique of constructing a public persona – that is perhaps different to one's true self, or private persona - in order to satisfy the demands imposed by society. This implies duplicity and disguise in the literary discourse. This study focuses mainly on the analysis of the female characters; special attention is given to the go-between. The characteristics of the medieval bawd and its Greco-Roman antecedents appear again in the new literary character of the female Spanish pícara of the XVI century. As in the case of the bawd, the pícara knows how to manipulate people regarding love, sex and greed. Through these marginal characters the authors voice their opinion regarding politics, religion and social conditions. Rojas, a converso living in Spain during the Inquisition, expresses his views in a veiled manner by criticizing and finding fault with Christian values. On the other hand, Castillejo, as in the case of Rojas, attacks the corruption of the Catholic Church and ridicules the sacrament of matrimony. Finally, these authors follow the traditional misogynistic views conceived by the church fathers. / Spanish