In Greek mythology, Brisēis (Greek Βρισηίς) was a Trojan widow (from Lyrnessus) who was abducted during the Trojan War by Achilles upon the death of her three brothers and husband, King Mynes of Lyrnessus, in the fight. After an oracle forced Agamemnon to give up Chryseis, a woman he had captured, the king ordered his heralds Talthybius and Eryrates to take Briseis from Achilles as compensation. Achilles was offended by this seizure and, as a result, withdrew from the fighting. He did not return to the fray until the death of Patroclus.
The retirement of Achilles to his tent is the first event of Homer's Iliad. With Achilles removed from the conflict, the Trojans enjoyed a period of success. After Achilles' return to the fighting, Agamemnon restored Briseis to Achilles.
Briseis's real name was Hippodameia, 'Briseis' being a patronym as a daughter of Briseus.