In Greek mythology, Pelasgus (Ancient Greek: Πελασγός) was the eponymous ancestor of the Pelasgians, the mythical inhabitants of Greece who established the worship of the Dodonaean Zeus, Hephaestus, the Cabeiri, and other divinities. In the different parts of the country once occupied by Pelasgians, there existed different traditions as to the origin and connection of Pelasgus. The ancient Greeks even used to believe that he was the first man.
In Argos, several Inachid kings were also called Pelasgus. One, the brother to Apis both sons of Phoroneus, is said to have founded the city of Argos in Peloponnesus, to have taught the people agriculture, and to have received Demeter, on her wanderings, at Argos, where his tomb was shown in later times. Another was believed to have been a son of Triopas and Sois, and a brother of Iasus, Agenor, and Xanthus. Also known as Pelasgus was Gelanor, he welcomed Danaus and the Danaides when they fled from Aegyptus. According to others, again, Pelasgus was a son of Arestor, and grandson of Iasus, and immigrated into Arcadia, where he founded the town of Parrhasia.
In Aeschylus' play The Suppliants the Danaids fleeing from Egypt seek asylum from King Pelasgus of Argos, which he says is on the Strymon including Perrhaebia in the north, Dodona and the slopes of the Pindus mountains on the west and the shores of the sea on the east; that is, a territory including or north of the Thessalian Pelasgiotis. The southern boundary is not mentioned; however, Apis is said to have come to Argos from Naupactus "across" (peras), implying that Argos includes all of east Greece from the north of Thessaly to the Peloponnesian Argos, where the Danaids are probably to be conceived as having landed. He claims to rule the Pelasgians and to be the "child of Palaichthon ('ancient earth') whom the earth brought forth."