John Doukas, Latinized as Ducas (Greek: Ἰωάννης Δούκας, romanized: Iōannēs Doúkas) is the name of several Byzantine aristocrats and their descendants. It may refer to any of the following:

• John Doukas (Caesar) (fl. 1074–1088), brother of Emperor Constantine X Doukas
• John Doukas (megas doux) (c. 1064 – before 1136), brother-in-law of Alexios I Komnenos
• John Doukas (megas hetaireiarches) (fl. 1155–1181), military commander and diplomat
• John Doukas (sebastokrator) (c. 1126 – c. 1200), cousin of Emperors Isaac II Angelos and Alexios III Angelos
• John Doukas Komnenos (1128–1176)
• John III Doukas Vatatzes (1193–1254), Emperor of Nicaea 1222–1254
• John Komnenos Doukas (d. 1244), ruler of Thessalonica and Thessaly 1237–1244
• John Doukas (son of Michael II), son of Michael II of Epirus, hostage in Constantinople
• John I Doukas of Thessaly, ruler of Thessaly 1268–1289
• John II Doukas of Thessaly, ruler of Thessaly 1303–1318
• John II Orsini (also called Doukas), ruler of Epirus 1323–1335
• John Uroš, ruler of Thessaly 1370–1373

This disambiguation page lists articles about people with the same name.
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