Among the most significant theologians in the history of the church, Thomas Aquinas surely stands near the top. Producing a massive corpus of biblical, theological, and philosophical material, few thinkers have left the church such a vast collection of writings. While he is most known for his magisterial Summa Theologica, Aquinas authored a large number of commentaries covering most of the New Testament and several books of the Old Testament. These works are not ancillary to his theological project, however, but are the product of a true theologian who views the Bible as the book of theology for the church (McGuckin). Among this understudied portion of Aquinas’ corpus, his Commentary on the Psalms has been particularly overlooked (Ryan). The commentary goes unaddressed in both monographs on medieval exegesis of the Psalms (Hendrix) and in handbooks of Aquinas’ own biblical commentaries (Weinandy, Keating, and Yocum). This unfortunate neglect is unwarranted, however, given that Aquinas views the Psalms as “contain[ing] the whole of Scripture” (Commentary Prol). Aquinas’ work on this biblical book deserves to be further studied, appreciated, and brought into conversation with modern biblical interpretation, for the Commentary on the Psalms offers profound insight into Aquinas’ exegetical methodology, revealing his expansive understanding of the literal sense, the importance of totus Christus, and a willingness to identify multiple meanings of a single biblical text. While these elements are present throughout the Commentary, I will limit my focus to Aquinas’ treatment of Psalm 21(22), given that this psalm “treat[s] the passion of Christ in detail” (Commentary 21.176) and contains multiple examples of Aquinas’ overall hermeneutical approach.