Euphrosyne Doukaina Kamaterina or better Kamatera (, – 1211) was a Byzantine Empress by marriage to the Byzantine Emperor Alexios III Angelos. Euphrosyne was the daughter of Andronikos Kamateros, a high-ranking official who held the titles of megas droungarios and pansebastos and wife, an unknown Kantakouzene. She was related to the Emperor Constantine X and Irene Doukaina, empress of Alexios I Komnenos. Both of her brothers had rebelled against Andronikos I Komnenos; one was imprisoned and the other was blinded. Life Euphrosyne married Alexios Angelos, the older brother of the future Emperor Isaac II Angelos in c. 1169. Although Isaac II bestowed many titles and honors upon his brother, Alexios seized the throne on April 8, 1195, deposing Isaac and proclaiming himself emperor. In this he was assisted by Euphrosyne, who had organized a party of aristocratic supporters. Euphrosyne took control of the palace and quelled the opposition herself, securing the accession of her husband to the throne by wholesale bribery. Euphrosyne was a dominating woman with a talent for politics, and she virtually ruled the Empire in the name of Alexios III, who was concerned primarily with pleasure and idle pursuits. She issued commands herself and even altered Alexios' decrees when it suited her, and secured the recall of the capable minister Constantine Mesopotamites. Euphrosyne and Alexios were criticized for their love of finery and the enrichment of their relatives at state expense. Her own brother, Basil Kamateros, and her son-in-law, Andronikos Kontostephanos, accused Euphrosyne of adultery with one of her ministers, a nobleman named Vatatzes. Alexios III believed the allegations and had Vatatzes executed. Euphrosyne was stripped of her imperial robes and banished to a convent at Nematarea in October 1196. However, her relatives convinced Alexios to reinstate her, and she was recalled six months later in spring 1197. In 1203, faced with the Fourth Crusade and the return of his nephew, Alexios IV Angelos, Alexios III fled Constantinople with a magnificent treasure and some female relatives, including his daughter Irene. Euphrosyne was left behind and was immediately imprisoned by the new regime. Alexios IV was soon strangled by Alexios Doukas Mourtzouphlos, the lover of Euphrosyne's daughter Eudokia, who then proclaimed himself emperor as Alexios V. In April 1204 Euphrosyne fled the city along with her daughter and Alexios V, and they made their way to Mosynopolis, where Euphrosyne's husband Alexios III had taken refuge. Alexios III had