Merope (Ancient Greek: Μερόπη) was a Queen of Messenia in Greek mythology, daughter of King Cypselus of Arcadia and wife of Cresphontes, the Heraclid king of Messenia. After the murder of her husband and her two older children by Polyphontes (another Heraclid), Merope was forced to marry the murderer, but she managed to save her youngest son Aepytus, whom she sent secretly to Aetolia. Several years later, when Aepytus grew up, he killed Polyphontes with the collaboration of Merope, and he took revenge for the murder of his relatives and the insult to his mother.
Euripides based his lost tragedy Cresphontes (Κρεσφόντης, Kresphóntēs) on this myth.
According to Hyginus' description of the plot (Fabulae 184), Merope's son (in this version also named Cresphontes), once grown, set in motion the plan to avenge his father's death by presenting himself incognito to Polyphontes as his own killer, claiming the price Polyphontes had put on his head. As the tired young man slept, "Merope, believing the sleeping man to be her son's murderer, came into the room with an axe, unwittingly intending to slay her own son".
Plutarch quotes a line spoken by Merope in this scene in his essay On Meat-Eating (Moralia 998e) and adds, "what a stir she rouses in the theatre as she brings them to their feet in terror lest she wound the youth before the old man [who had served as secret messenger between mother and son] can stop her!"
Aristotle cites this as an intended action that would have been performed involuntarily due to Merope's ignorance of the particular circumstances of the action: "one might think one's son was an enemy, as Merope did" (Nicomachean Ethics III.1, 1111a11-12, trans. Ross). Hyginus continues: "When Merope realised her enemy had given her the opportunity of avenging herself, she made things up with Polyphontes. As the joyful king was performing a religious ceremony his guest, falsely pretending to have killed the victim, killed him and regained his paternal kingdom."