The church uses the doctrine of the Trinity for many things that we might call internal to the church: catechesis, systematics, worship, spiritual formation, and hermeneutics. But the doctrine also has a function toward those outside the Christian faith, especially in apologetics. This paper is a high-level survey of the aspects of trinitarian doctrine that come to the fore when we approach it from the point of view of the church’s apologetic task. These aspects include (1) the Trinity as truth that is revealed rather than being available to natural reason; (2) the Trinity as a synthetic claim assembled from the full canon of Scripture; (3) the Trinity as a means of identifying God, or specifying the God who Christian theology is about. In light of these three apologetic aspects of the doctrine, the paper concludes by considering how apologetics is helpful for trinitarian theology (apologetics plays a key role in surfacing truth claims, removing obfuscation, and stating a clear public position on the meaning of Scripture), and how it presents certain temptations for trinitarian theology (apologetics may draw some theologians to simplify, distort, or over-explain crucial elements of the doctrine of God).