Demetrios Komnenos Doukas

Demetrios Komnenos Doukas, Latinized as Comnenus Ducas (Greek: Δημήτριος Κομνηνός Δούκας), was ruler of Thessalonica from 1244 until his deposition in 1246. He was born c. 1220.

Demetrios was the younger son of Theodore Komnenos Doukas and Maria Petraliphaina. In 1230 his father was captured together with his family in the Battle of Klokotnitsa by Ivan Asen II of Bulgaria. When his sister Irene married Ivan Asen II in 1237, Demetrios was released from captivity together with his now blind father Theodore and his older brother John. Theodore and his sons made their way back to Thessalonica and incited a revolt against Theodore's brother Manuel Komnenos Doukas who had ruled the city since 1230. Since Theodore was blind, he installed his son John as ruler and retired to Vodena. When John submitted to Emperor John III Doukas Vatatzes of Nicaea in 1242, Demetrios also received the title of despotes.

Demetrios succeeded his brother as ruler of Thessalonica in 1244. Young and dissolute, Demetrios inspired little loyalty among the leading families of Thessalonica. When Emperor John III Doukas Vatatzes campaigned near the city during his invasion of Bulgaria in 1246, the local nobility conspired to arrest Demetrios and turn over the city to the Nicaean emperor. Demetrios was powerless to resist and the city was surrendered to John III Doukas Vatatzes. Demetrios was sent into exile to the fortress of Lentiana. The date of his death is unknown.