The purpose of this dissertation is to produce a critical edition of Álvaro de Luna's 15th century manuscript, Libro de las claras e virtuosas mugeres. This Castilian text is a compilation of biographies of good and virtuous women similar to that of the widely studied De claris mulieribus by Giovanni Boccaccio. Scholars however, have neglected Luna's version for various reasons that are discussed within this dissertation. Libro de las claras e virtuosas mugeres is a significant work because it complements other texts within the genre of defense literature and provides a good argument against the misogynistic texts in the debate on women in the Middle Ages. Within this dissertation, the Introduction serves to orient the reader through the debate on women in 15th century Castile and to contextualize the Libro de las claras e virtuosas mugeres within it. Through the discussion of the debate on women in medieval Iberia, we will show how Luna's work is a necessary, but forgotten element. Also pertinent is the notorious past of don Álvaro, and how this has negatively impacted the reception of his work. This dissertation also compiles all critical studies and editions currently in print and discusses their merits. Finally in the Introduction, we explain how we took into account Bernard Cerquiglini's concept of variance and John Dagenais' theory that in order to come close to the medieval reading of the text, it is necessary to replicate the manuscripts, not to modernize them. Thus, we produced transcriptions that were as close to the original texts as possible, rather than attempting to correct or modernize them. In order to produce the critical edition necessary for a proper study of the Libro de las claras e virtuosas mugeres, this dissertation contains two transcriptions of the two oldest extant manuscripts: ms. B (2654) and ms. S (207). Within ms. B we also provide a critical apparatus, which shows the lexical and orthographical differences between the two. Additionally for the benefit of the reader, we provide four Appendices: the missing chapter of the Queen of Sheba (not included in ms. B), a list of all the women Luna included in his work, and facsimilar samples of both manuscripts. It is our desire to promote a renewed interest in this forgotten, yet extremely important 15th century Castilian manuscript. / Spanish