Megareus of Thebes was one of the participants in the battle of the Seven Against Thebes. In the myth, the twin brothers Eteocles and Polynices march against each other in a struggle to take the throne of the city. The war erupted after Eteocles kept the throne for himself, although he had previously agreed that he would share the throne with his brother.
Megareus was the son of Creon and Eurydice, brother of Haemon, Antigone and Ismene, and uncle of the two main characters. His father was in favour of Eteocles, but did not want his son to participate in the war, afraid he might be killed. A prophecy by Teiresias informed Creon that the only way for Eteocles to win would be if Megareus would be sacrificed. Creon decided to ignore the prophecy and sent his son away from the city. Despite Creon's attempts, Megareus nevertheless joined the battle, as it was unbearable for him to be considered a coward; he was killed in the first battle.