In Greek mythology, Pelopia (or Pelopea or Pelopeia; ) was a name attributed to four individuals:

Pelopia, less commonly known as Mnesiphae, was the daughter of Thyestes. Thyestes had been fighting with his brother, Atreus, for the throne of Mycenae for some time, as well as having an affair with Atreus' wife, Aerope. In vengeance for the affair, Atreus killed Thyestes' sons and served them to him at a banquet. Thyestes swore vengeance. An oracle then advised Thyestes that, if he had a son with his own daughter, Pelopia, that son would kill Atreus. So when Pelopia, who at the time stayed in Sicyon at the court of king Thesprotus, came to the bank of a river to wash her clothes that had been stained with blood during a sacrificial rite, Thyestes, covering his face, attacked and raped her. She managed to pull out his sword and kept it so she could recognize her offender. Soon after that, Atreus came to Thesprotus in search of his brother and, taking Pelopia for a daughter of Thesprotus, asked for her hand, to which Thesprotus consented in order not to reveal the truth.