John Doukas, Latinized as Ducas (; – ), was the eldest son of Constantine Angelos by Theodora Komnene, the seventh child of the Byzantine Emperor Alexios I Komnenos and Irene Doukaina. John Doukas took the family name of his grandmother Irene. He served as a military commander under Manuel I Komnenos and Isaac II Angelos. Isaac II, who was Doukas's nephew, raised him to the high rank of "sebastokrator". Despite his advanced age, he continued to be an active general in the 1180s and 1190s, and until shortly before his death aspired to the imperial throne. He was the progenitor of the Komnenos Doukas line, which founded the Despotate of Epirus after the Fourth Crusade.