This article presents a reconstruction of an important but neglected element of the trinitarian theology of Thomas Aquinas: namely, his teaching on the notional acts, the intratrinitarian acts attributed to the Divine Persons, and how they relate to individual Divine Persons. In the process, this article shows that, for Aquinas, and for medieval theologians more generally, although we can distinguish between the Divine Persons and their respective intratrinitarian acts according to our human mode of understanding, each Divine Person is, in reality (literally, in the res, or in the thing), nothing other than a single eternal act. This article also explains how thinking of the Divine Persons as divine acts offers significant resources for contemporary theology and corrects against certain perceived weaknesses of Aquinas’s trinitarian theology and relation-centered accounts of the Trinity more generally.