This thesis investigates Thucydides’ representation of Greek religion in his account of the Peloponnesian War. It demonstrates that Thucydides did not suppress the ‘religious war for the hearts and minds’ of the Greeks (Hornblower, 1992). In Thucydides, religion informs the outlook of the historical characters by shaping their perception of the world around beliefs about the gods, hope, and fortune, among other religious concepts. In disastrous moments, religious language and ideas are manifested in the speeches and actions of his characters as they make sense of their situation and respond to the threat or impact of military defeat. Thucydides uses a tragic model of writing history to guide his audience into emotive and reflective readings of his disaster narratives. By drawing on tragic themes that support the dramatic portrayal of life in Attic tragedy, Thucydides presents the ancient Greeks’ experience of daily life as it was informed by their religious outlook. Thucydides reveals that he conceptualised structures of religious understanding in a manner similarly displayed in tragedy, and while he seems to encourage some tragic resonance, his method is independent. The accounts of four disasters exemplify Thucydides’ use of a tragic model: the siege and trial of Plataea, the Athenians’ fortification of the sanctuary of Apollo at Delium, the Melian Dialogue, and the Sicilian Expedition. Through these disaster narratives, Thucydides displays the religious dimension of the war that greatly influenced the lives of those involved.