DUCAS, DUKAS or DOUKAS, the name of a Byzantine family which supplied several rulers to the Eastern empire. The family first came into prominence during the 9th century, but was ruined when Constantine Ducas, a son of the general Androni cus Ducas, lost his life in his effort to obtain the imperial crown in 913. Towards the end of the loth century there appeared an other family of Ducas, which was perhaps connected with the earlier family through the female line. A member of this family became emperor as Constantine X. in Io59, and Constantine's son Michael VII. ruled, nominally in conjunction with his younger brothers, Andronicus and Constantine, from 1071 to 1078. Mi chael left a son, Constantine, who married into the family, which was also allied by marriage with other great Byzantine houses, and its members continued to take an active part in public affairs. In 1204 Alexius Ducas, called Mourzoufle, deposed the emperor Isaac Angelus and his son Alexius, and vainly tried to defend Constantinople against the attacks of the Latin crusaders. Nearly a century and a half later one Michael Ducas took a leading part in the civil war between the emperors John V. Palaeologus and John VI. Cantacuzenus, and Michael's grandson was the historian Ducas (see below). Many of the petty sovereigns who arose after the destruction of the Eastern empire sought to gain prestige by adding the famous name of Ducas to their own.