In Greek mythology, Brisêis was a Trojan widow (from Lyrnessos ) who was abducted during the Trojan War by Achilles after the death of her husband Mines and brother in the fight. After an oracle forced Agamemnon to give up a woman he had captured, Chryseis, Agamemnon ordered his heralds Talthybius and Eryrates to take Briseis to compensate himself. Achilles was offended by this seizure, pouted, and refused to fight until his prize was restored, leading to many of the most important events of the Trojan War, including the death of Patroclus.

The withdrawal of Achilles to his tent in protest of the loss of Briseis is the first event of Homer's Iliad. With Achilles on the sidelines, the Trojans had a period of success. When Agamemnon restored Briseis to Achilles, he swore that he had not offended her chastity.