This chapter examines the religious role of Alexander as king and military commander in the Greek world and the territory of the Achaemenid empire. It explores how he used sanctuaries of the gods to develop his relationship with the Greek cities, as locations for the meetings of associations of Greek cities, and as sites for making dedications. It considers the honours offered to Alexander by the Greek cities, arguing that these were offered spontaneously, and were not a response to any request from Alexander. It discusses his use of diviners and other religious experts while on campaign. It considers the extent to which Alexander engaged with the religious practices and expectations of the territories he conquered, including in particular Egypt and Babylon. It discusses the evidence that Alexander consciously attempted to emulate Heracles and Dionysus, and suggests that this is unlikely to reflect any historical reality. It then explores the story of Alexander’s visit to the oracle of Ammon/Amun at the Siwah oasis, suggesting that while Alexander was aware of the significance of his pharaonic titulary, including the phrase ‘son of Amun’, this did not lead to claims of divine filiation beyond Egypt.