Pelasgus gave his name to the Pelasgians, the aboriginal inhabitants of Greece. According to Aeschylus he was a king of Argos, possibly a son of Zeus and Niobe. His name is usually related to either palaios, 'ancient' or pelagos, 'sea'.

Pelasgus would have been 'ancient' as the ancestor of the people who inhabited Greece before the Greeks; almost any Greek (or Pelasgian) could have regarded himself as someone whose life and destiny was never too far removed from the 'sea'.