In Greek mythology, Tydeus (Τυδεύς) was the father of Diomedes and husband of Deipyle. He was a son of Oeneus and either Periboea, Oeneus's second wife, or Gorge, Oeneus's daughter. He was one of the Seven Against Thebes; during the battle to take the city, he was killed by Melanippus.
Tydeus was banished from Calydon by his uncle Agrius, because he killed either his brother or a different uncle or eight of his cousins. He travelled to Argos, where he married the Deipyle, the daughter of king Adrastus. The king agreed to help Tydeus regain the rule of Calydon, but chose to first help Polynices regain the kingship of Thebes.
Seven against Thebes
In the Iliad, Homer alludes several times to Tydeus's role in the attack on Thebes. Before the fighting began, Tydeus was sent into the city bearing a message for the Cadmeians. He found them feasting in the house of Eteocles, and challenged them to contests, all of which he won with the help of Athena. Enraged, the leaders sent a force of fifty men to attack Tydeus on his way back to the army, with Maion and Polyphontes leading them. Tydeus killed all of them but Maion, whom Athena advised him to spare.
In the attack on Thebes, Tydeus was severely wounded by Melanippus, but killed him and ate his brains. This shocked Athena, who would have made him immortal.