In Greek mythology, Myrmidon was the eponymous ancestor of the Myrmidons.
He was the son of Zeus and Eurymedusa, daughter of Cleitor (Cletor) of Arcadia or of the river god Achelous. Zeus was said to have approached Eurymedusa in the form of an ant (Greek μύρμηξ myrmēx), which was where her son's name came from; others say that Myrmex was the name of Eurymedusa's mortal husband, and that it was his shape that Zeus assumed to approach her.
Myrmidon married Peisidice, daughter of Aeolus and Enarete, and by her became the father of Antiphus and Actor. Also given as his sons are Erysichthon and Dioplethes, himself father of Perieres, although Erysichthon and Perieres have been ascribed different parentage as well. He also had two daughters: Eupolemeia (mother of the Argonaut Aethalides by Hermes) and Hiscilla (mother of Phorbas by Triopas).