Thyestes is a play by the ancient Roman playwright Lucius Annaeus Seneca in style of earlier Greek tragedies. The play winds a twisted tale of revenge between two warring brothers who are the rulers of their kingdom. The tale begins with the history of the family, with grandfather Tantalus having passed away and his son Pelops having banished his children, Atreus and Thyestes, for murdering their half-brother Chrysippus. When Pelops passes away, both brothers lay claim to the throne, but Thyestes steals a magical beast from Atreus and sleeps with his brother's wife, Aerope. Because of all this, Atreus banishes him but plots a far greater revenge.

The story of the actual play begins when Tantalus is revived from death and begins to stir the controversy between his grandsons. Atreus begins asking for advice on how best to take revenge on his brother but is met mostly with counsel to do the right thing and let the matter rest. Atreus refuses and devises a devious and terrifying plan. Atreus takes Thyestes's sons hostage in order to ensure that he returns, but he secretly has the boys executed instead of planning to return them as promised. Knowing his sons are imprisoned, Thyestes comes to visit Atreus. Upon his brother's arrival, Atreus throws a lavish feast in his honor. The Chorus and muses who have been interjecting throughout the story predict the horror and fear the world itself will collapse with the vile deed that is about to happen.

After eating the feast, Atreus enacts his revenge. He reveals to his brother Thyestes that he will not return his sons in the manner promised. In fact, the sons have already been returned—Atreus used them to create the feast set before them, and Thyestes has unwittingly been consuming his own children's dead bodies. This is one of the more vile and despicable acts of revenge in ancient literature, but the shocking nature makes it all the more memorable.