John Doukas (Greek: Ἰωάννης Δούκας, romanized: Iōannēs Doúkas; fl.
1155/6–1181) was a senior Byzantine military commander and diplomat under Manuel I Komnenos, serving in Italy, Hungary, Asia Minor, and the Holy Land.
[5][6] The first activity which can be more or less securely attributed to John Doukas is an embassy to the Holy Roman Emperor Frederick I Barbarossa in 1155/6, followed by his stay in Italy.
[9] Another scholar, the philosopher Constantine of Nicaea, wrote a consolatio on the death of John's wife, praising her interest in "real philosophy" (ascetic virtue).
He may be the John Doukas that Niketas Choniates has him defending Nicaea unsuccessfully against Andronikos Komnenos in 1182.