John Doukas
John Doukas, Latinized as Ducas is the name of several Byzantine aristocrats and their descendants. It may refer to any of the following:
- John Doukas (Caesar), brother of Emperor Constantine X Doukas
- John Doukas (megas doux), brother-in-law of Alexios I Komnenos
- John Doukas (son of Nikephoros Bryennios), military commander, son of Anna Komnene and Nikephoros Bryennios
- John Doukas (megas hetaireiarches), military commander and diplomat
- John Doukas (sebastokrator), uncle of Emperors Isaac II Angelos and Alexios III Angelos
- John Doukas Komnenos
- John III Doukas Vatatzes, Emperor of Nicaea 1222–1254
- John Komnenos Doukas, 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, ruler of Epirus 1323–1335
- John Uroš, ruler of Thessaly 1370–1373