This dissertation offers the first English translation of the treatise *De natura et gratia* by the Spanish Dominican Domingo de Soto (c. 1494-1560), published shortly after his initial tenure at Trent during the first period of the Council. The treatise examines four "states" of humanity (the state of pure nature, the state of original justice, the fallen state, and the justified state) in fifty-seven chapters across three books. While Soto himself styles the treatise as an exposition and defense of the Fifth and Sixth Sessions of the Council of Trent, it mainly aims at refuting Lutheran teaching and, even more, presenting Thomistic soteriology in light of the Reformation controversies. Along with the translation (Appendix B), the dissertation also provides a Latin text of *De natura et gratia* (Appendix A), a comparison of significant differences between the first printing of the treatise and two subsequent printings (Appendix C), and an introduction to the treatise (Chapters 1-3). The first chapter of the introduction explores Soto's involvement at the Council of Trent and its bearing upon *De natura et gratia*. The first chapter thus also considers Soto's explicit interaction with the Council of Trent's decrees concerning original sin (Fifth Session) and justification (Sixth Session). The second chapter of the introduction examines Soto's engagement with Lutherans, while the third chapter offers an overview of Soto's approach to Scripture, the Fathers, various medieval figures, and his own Catholic contemporaries.