Eris is the daughter of Nyx or of Zeus and Hera. Some also claim that she and her twin-brother Ares were conceived when Hera touched a flower (probably a may-blossom). She is also sister to Eileithyia, and Hebe. Eris was the personification of discord and strife, so she often accompanied her brother Ares (the god of war) by being the cause of wars. She would spread rumors among men for the mere pleasure of watching the bloody struggles of others.

Her most infamous role in mythology is setting off the chain of events that caused the Trojan War. When Eris was not invited to the wedding of Peleus and Thetis, she decided to extract her revenge on the other gods and goddesses. She took one of the golden apples of the Hesperides and carved into it the word "Kallisti" ("For the fairest"). She tossed it among the wedding guests, and Peleus, the groom, spotted it first. Hera, Athena, and Aphrodite all claimed the apple, but Zeus refused to decide whose it was and gave the task to the Trojan prince Paris. Paris then kidnapped the Spartan queen, Helen, as his prize for selecting Aphrodite (who had an affair with Ares) which caused Menelaus, the king of Sparta, to sail against Troy and attack the city for ten years.

Along with her brother Ares, Eris was later not invited to the wedding of Pirithous and Hippodamia, so they had a group of centaurs attack the guests and begin the long feud between the Lapiths and centaurs. Eris also is noted for helping Zeus when he reversed the course of the sun and stars after Thyestes declared that he would abdicate the throne to Atreus if such a phenomenon should occur.

Eris was the mother of Algos, Amphilogia, Androktasia, Dusnomia, Husmine, Lethe, Limos, Logos, Mache, Neikos, Phonos, Ponos, and Pseudes and had Ate by Zeus.