John Xiphilinos was a monk and scholar in Constantinople active in the second half of the eleventh century. During the reign of Michael VII Doukas (1071– 1078), Xiphilinos made a summary of Books 36– 80 of Cassius Dio's history of Rome, covering the years 68 BCE to 229 CE.

In the midst of his summary of Dio, he pauses to identify himself as the nephew of the Patriarch John, writing during the reign of Michael Doukas. This refers to John Xiphilinos who was patriarch from 1064– 1075. John Xiphilinos the historian also wrote fifty- three homilies and a menologion dedicated to Alexios Komnenos (1081– 1118) that survives only in a Georgian translation. Although we do not have birth or death dates for the historian, we can tell that he was writing in the 1070s and 1080s.

Although Xiphilinos worked mostly by cutting Dio's text, his changes to the material were thoughtful and work to focus his history far more on the moral character of the actors in history, particularly emperors. His interest in a summary history of the early Roman emperors can be seen as part of an intellectual trend in the late eleventh century. Xiphilinos shortens Dio's text considerably, omitting many, but not all, speeches. He seems to have kept speeches and exposition that reflect on the proper behavior of emperors. Dio's authorial interjections about himself are retained in the summary, but Xiphilinos also added his own, clarifying which historian was speaking. Mallan argues that this reflects the trend in eleventh- century history writing for historians to comment on the action in their own voice. Xiphilinos kept nearly all of Dio's quotations from Homer and ancient drama, and his own additions often work to display his classical erudition. His version of Dio is less interested in constitutional issues than in presenting models of good and bad behavior. Xiphilinos adjusts the organizational structure of Dio's history to be a series of portraits of individual emperors, rather than Dio's somewhat more annalistic style. This is in keeping with the trend in Byzantine history writing to treat the past as a series of biographies of emperors.