John Doukas or Ducas (Greek: Ιωάννης Δούκας, Iōannēs Doukas), (c. 1126 – c. 1200) was the eldest son of Constantine Angelos by Theodora Komnene, the seventh child of the Byzantine Emperor Alexios I Komnenos and Irene Doukaina, from whose family name John Doukas took his own.