Olympias was an Epiran princess, a wife of Philip of Macedon and the mother of Alexander the Great. According to several legends, Olympias was impregnated not by Philip, who was afraid of her and her affinity for sleeping in the company of snakes, but by Zeus. Alexander was himself aware of these legends, and was wont to refer to his father as Zeus, rather than Philip.
By tradition Olympias was descended from another woman of the same name, daughter of Neoptolemus and Andromache and so grand-daughter of Achilles. This formed the basis of Alexander's claims to be a new Achilles.