Myrtale probably took the name Olympias, the third of four names by which she will be known, as a recognition of Philip's horse-race victory in the Olympic Games of 356 BCE, the news of which coincided with the birth of her first child, who will become known to posterity as Alexander the Great. (Plut. Alexander 3.8).

In ancient Greece people believe that the birth of a great man is accompanied by portents.

As Plutarch describes, the night before the consummation of their marriage Olympias had dreamed that a thunderbolt fell upon her womb and a great fire was kindled, its flames dispersed all about, then extinguished.

After the marriage Philip had dreamed that he put a seal upon his wife's womb, the device of which was the figure of a lion.

The interpretation of Aristander, a seer in Philip's entourage, had been that Olympias was pregnant of a son whose nature would be bold and lion-like.