Abstract: We live in the best possible world, says the theory of divine providence, because events in the world occur in accordance with the plans of a deity benevolent towards human beings. It was the early Stoics who first formulated a robust version of this theory; my thesis investigates this formulation, first within the context of earlier Greek speculation about the relationship between the gods and the physical world, and then within the context of other aspects of Stoic thought. Chapter 1 demonstrates that the Presocratics---contrary to prevailing scholarly views---have little interest in reasoning or planning as a cause of order in the cosmos. Such interest develops in the fourth century BC, as I show in Chapters 2 and 3. Xenophon, in two texts that greatly influenced the Stoics, represents Socrates as arguing, on the basis of apparent design in nature, that god is a wise and benevolent craftsman of animals; and that the universe is anthropocentric, designed at the cosmic level to be a suitable environment for humans to thrive. Plato develops in Laws Book 10 and the Timaeus accounts of a god, identified wholly with reason, who maximizes good in the world. The Timaeus also offers the Stoics a model for a physical theory that shows how the world is controllable by god on an event-by-event basis. Chapters 4 and 5 focus on the second book of Cicero's De natura deorum, which offers more insight than scholars have previously realized into both the method and content of early Stoic theology. First, god's existence is established. It is then argued that god is to be identified with the unifying, rational nature of the cosmos as a whole (the existence of which is argued by inference). The Stoics' key claim is that ''providence'' names god's rational agency. God's life, like any animal's life, is constituted out of particular actions. Since god comprises all parts of the cosmos, god’s actions structure the world into a nexus of events under divine administration. The recovery of this argumentation promises interesting consequences for our understanding of Stoic ethics.