This Element is an overview of the Catholic conception of God and of philosophical problems regarding God that arose during its historical development. After summarizing key Catholic doctrines, the first section considers problems regarding God that arose because Catholicism originally drew on both Jewish and Greek conceptions of God. The second section turns to controversies regarding God as Trinitarian and incarnate, which arose in early church councils, with reference to how that conception developed during the Middle Ages. In the third section, the author considers problems regarding God's actions towards creatures, including creation, providence, predestination, and the nature of divine action in itself. Finally, the last section considers problems regarding how we relate to God. The Element focuses on tensions among different Catholic spiritualities, and on problems having to do with analogical language about God and human desire for God.