This study brings together the works of Giovanni Boccaccio (1313-1375) and Gratian’s Decretum, the 12th-century textbook that became foundational to the teaching of medieval canon law. Boccaccio studied canon law for six years, and the Church’s legal system deals with many of the issues that interested Boccaccio: marriage, sexuality, adultery, consent, coercion, and gendered forms of violence. Boccaccio and Gratian each showed close attention to women’s interior perspectives and a marked emphasis on the importance of consent. This dissertation illuminates the intertextual connections between Boccaccio’s works and Gratian’s Decretum, and argues that Boccaccio understand the law much better than has previously been recognized. In fact, Boccaccio’s most perceptive insights on the nature of debt, obligation, and consent derive from legal sources. The first chapter of this project introduces the figures of Boccaccio and Gratian. Boccaccio’s own works and a few surviving documents attest to his years of legal study in Naples as well as his lifelong engagement with the law, both in politics and his personal life. Little is known of Gratian’s biography, but his Decretum became a standard teaching tool in the curriculum of canon law. Boccaccio undoubtedly read the Decretum, and the following chapters show the extent to which its innovative cases and viewpoints influenced him. Chapter 2 begins with the “conjugal debt,” the idea in canon law that spouses incur a mutual sexual obligation by virtue of being married. Boccaccio expands the concept of sexual debt to include metaphorical usury and theft, drawing on medieval economic theory and offering an economic model of human relationships. Though Boccaccio’s view is transactional, it does not reduce human beings to commodities; rather, the economic system expresses relationships of trust and obligation. Chapter 3 extends the legal-economic discourse to several stories in the Decameron that deal with adulterous relationships, demonstrating that Boccaccio’s idiosyncratic application of legal theories is nevertheless solidly grounded in his reading of canon law. Chapter 4 focuses on Boccaccio’s treatment of consent in matters of marriage and legislation. Relying heavily on Gratian’s treatment of error and mistaken identity, as well as the legal principle of quod omnes tangit, Boccaccio argues for women’s right to offer informed consent to decisions that concern them. Chapter 5 continues the discussion of consent in the context of sexual violence, exploring the idea of vis (force) in Gratian’s Decretum as well as Boccaccio’s Decameron and Ninfale fiesolano. Canon law emphasizes women’s right to consent to marriage; Boccaccio extends this principle to matters of sex and violence, recuperating the power of women’s consent in an area where medieval law often faltered.