This is a study of the Byzantine novel or Milesian tale in Spain during the 17th century. It contains a brief comment about the origin of this literary mode and the significance of the two adjectives Byzantine and Milesian. Two novels of the Hellenistic originators of this form are discussed. Four Spanish Byzantine novels are considered in chronological order, with summaries and analyses, with particular attention to their similarity to or modification of the prototypes. It is concluded that this particular aspect of 17th century Spanish fiction is a deliberate imitation of the Hellenistic models, modified by the Spanish authors by the addition of original and contemporary ideas. No longer a popular genre, the Byzantine novel made a significant contribution to the development of the modern Spanish novel.