The article aims to give an overall overview of St Augustine's attitude towards the Gnostic-Christian Manichaeans. First, a historical overview, mainly based on his Confessions, outlines Augustine's acquaintance with the members of the Manichaean Church and his familiarity with their writings. Second, the place of the Manichaeans in a considerable number of Augustine's other works is discussed. It is in particular in his many anti-Manichaean writings that the Church Father displays his intimate knowledge of the Manichaeans' myth and their doctrines. Third, a summary is given of the research on the impact of the Manichaeans on Augustine. It is concluded that, from his early years onwards and to the very end of his life, the Manichaean Christians were a real and powerful force to him.