This article attempts to redress the neglect of Sartre's relationship to Augustine, putting forward a reading of the early Sartre as an atheist who appropriated concepts from Augustinian theology. In particular, it is argued, Sartre owes a debt to the Augustinian doctrine of original sin. Sartre's portrait of human reality in Being and Nothingness is bleak: consciousness is lack; self-knowledge is impossible; and to turn to the human other is to face the imprisonment of an objectifying gaze. But this has recognizable antecedents in Augustine's account of the condition of human fallenness. The article, therefore, (a) demonstrates the significant similarities between Sartre's ontology of human freedom and Augustine's ontology of human sin; and (b) asks whether Sartre's project – as defined in Existentialism Is a Humanism – 'to draw the full conclusions from a consistently atheistic position' – results in a vision of the world without God, but not without sin. It is proposed that this opens the possibility for a previously unexplored theological reading of Sartre's early work.