Richard August Reitzenstein (2 April 1861, Breslau – 23 March 1931, Göttingen) was a German classical philologist and scholar of Ancient Greek religion, hermetism and Gnosticism. He is described by Kurt Rudolph as “one of the most stimulating Gnostic scholars.” With Wilhelm Bousset, he was one of the major figures of the Religionsgeschichtliche Schule (history of religions school).
His Poimandres: Studien zur Griechisch-Ägyptischen und frühchristlichen Literatur of 1904 was a pioneer scholarly study of the Poimandres, which he compared to the Shepherd of Hermas.
In collaboration with the German Egyptologist Wilhelm Spiegelberg, Richard August Reitzenstein founded a famous collection of Greek and Egyptian papyri, purchased during an expedition in Egypt in 1898/99.
Bousset, then Reitzenstein along with Rudolf Bultmann, were notable for promoting theories of pre-Christian gnosticism, and the influence of gnosticism on the New Testament. Modern scholars now reject these theories, while acknowledging that many of the features of later Christian gnosticism can be drawn from pre-Christian Jewish and Hellenistic roots.