AEGISTHUS, in Greek legend the son of Thyestes by his own daughter Pelopia (Hyginus, fab. 88). Having been exposed by his mother, he was found by shepherds and suckled by a goat (a1.), whence his name. His uncle Atreus, who had married Pelopia, took him to Mycenae, and brought him up as his own son. For the rest of his story see AGAMEMNON ; ATREUS.