John Komnenos Doukas (Greek: Ιωάννης Κομνηνός Δούκας, Iōannēs Komnēnos Doúkas), Latinized as Comnenus Ducas, was ruler of Thessalonica from 1237 until his death in 1244.

When his sister Irene married Ivan Asen II in 1237, John was released from captivity together with his now blind father Theodore and his younger brother Demetrios.

This and his exposed position attracted the attention of Emperor John III Doukas Vatatzes of Nicaea.

John was easily induced to content himself with the title of despotes and to recognize the suzerainty of Nicaea.

Securing these concessions, John III Doukas Vatatzes rapidly returned to Asia Minor to combat the invading Seljuk Turks.