Proetus (Greek: Προῖτος) was a mythical king of Argos and Tiryns. According to one source he was father of Perseus. His father Abas, son of the last surviving Aegyptiad Lynceus and the Danaid Hypermnestra, had ruled over Argos and married Aglaea or Ocalea, who bore him twin sons, Proetus and Acrisius, who quarreled continually ever since they still were in the womb. They carried on with the rivalry into their adult years, inventing shields or bucklers in the process. In one tradition, the conflict was reiterated when Proetus seduced Acrisius' daughter (and his own niece) Danae. Proetus started out as king of Argos, and held the throne for about seventeen years, but Acrisius defeated and exiled him and he fled to King Jobates or Amphianax in Lycia, and married his daughter Antea or Stheneboea. Jobates, thereupon, attempted to restore Proetus to his kingdom by armed force. After the war had gone on for a while the kingdom was divided in two. Acrisius then shared his kingdom with his brother, surrendering to him Tiryns and the eastern half of Argolis, i.e. the Heraeum, Midea and the coast of Argolis.
By his wife Proetus became the father of three daughters (the so-called Proitides) and a son Megapenthes. The daughters' names are Lysippe, Iphinoe, and Iphianassa in the Bibliotheca; Servius calls the last two Hipponoe and Cyrianassa, whereas Aelian only mentions two, Elege and Celaene. When these daughters arrived at the age of maturity, they were stricken with madness, the cause of which is differently stated by different authors; some say that it was a punishment inflicted upon them by Dionysus, because they had despised his worship. Others have assumed the troubles arose by Hera, because they presumed to be more beautiful than the goddess, or perhaps because they had stolen some of the gold off her statue. In this state of madness they wandered through Peloponnesus. Melampus promised to cure them, if Proetus would give him one third of his kingdom. As Proetus refused to accept these terms, the madness of his daughters not only increased, but was communicated to the other Argive women also, so that they murdered their own children and ran about in a state of frenzy. Proetus then declared himself willing to listen to the proposal of Melampus; but the latter now also demanded for his brother Bias an equal share of the kingdom of Argos. Proetus consented and Melampus, having chosen the most robust among the young men, gave chase to the mad women, amid shouting and dancing, and drove them as far as Sicyon. During this pursuit, Iphinoe, one of the daughters of Proetus, died, but the two others were cured by Melampus by means of purifications, and were then married to Melampus and Bias. There was a tradition that Proetus had founded a sanctuary of Hera, between Sicyon and Titane, and one of Apollo at Sicyon. The place where the cure was effected upon his daughters is not the same in all traditions, some mentioning the well Anigros, others the well Cleitor in Arcadia, or Lusi in Arcadia. Some even state that the Proetides were cured by Asclepius or that they were cured in the Cave of the Lakes.