Basil Argyros is the eponymous main character of a sequence of short stories (by Harry Turtledove) set in an alternate 13th Century. In this universe, the Prophet Muhammad, instead of developing Islam, converts to Christianity. As such, by the time the stories take place, the Eastern Roman Emperor is still the pre-eminent power in the Mediterranean world, and has reconquered much of Europe and Africa. Harry Turtledove (born June 14, 1949), is a historian and prolific novelist who has written historical fiction, fantasy, and science fiction works. ... (12th century - 13th century - 14th century - other centuries) As a means of recording the passage of time, the 13th century was that century which lasted from 1201 to 1300. ... Muhammad is a common male name for Muslims. ... Islam (Arabic al-islām الإسلام,  listen) the submission to God is a monotheistic faith and the worlds second-largest religion. ... Christianity is an Abrahamic religion based on the life, teachings, death by crucifixion, and resurrection of Jesus of Nazareth as described in the New Testament. ... This is a list of Byzantine Emperors. ...

Basil works as an agent for the Roman Emperor, and as such is sent across the Empire to solve problems - sometimes as a spy, sometimes as a negotiator, and sometimes as a soldier.

Stories in the Basil Argyros universe (in order written) are:

• Unholy Trinity
• Archetypes
• The Eyes of Argos
• Strange Eruptions
• Images
• Superwine
• Pillar of Cloud, Pillar of Fire

Most of the above were collected into a single book, Agent of Byzantium. An additional story in the universe, Departures, was written by Turtledove; Basil was absent from it as it took place hundreds of years earlier, and focused on the future St. Mohammed.