The Ptolemaic cult of Alexander the Great was an imperial cult in ancient Egypt in the Hellenistic period (323–31 BC), promoted by the Ptolemaic dynasty. The core of the cult was the worship of the deified conqueror-king Alexander the Great, which eventually formed the basis for the ruler cult of the Ptolemies themselves. The head priest of the cult was the chief priest in the Ptolemaic Kingdom, and years were dated after the incumbents (eponymous priests)[clarification needed].