In Greek mythology, Megapenthes (/ˌmɛɡəˈpɛnˌθiːz/; Ancient Greek: Μεγαπένθης Megapénthēs means "great sorrow") was a king of Argos and the son of Proetus[1] and exchanged kingdoms (Argos for Tiryns) with his cousin Perseus,[2][3] whom he killed much later.[4] He was the father of Argeus and possibly Anaxagoras (or else Anaxagoras was his grandson through Argeus). He also had a daughter Iphianeira, who married Melampus.[5][6]