Philostorgius (born 368 C.E.) was a member of the Eunomian sect of Christianity, a nonconformist faction deeply opposed to the form of Christianity adopted by the Roman government as the official religion of its empire. He wrote his twelve-book Church History, the critical edition of the surviving remnants of which is presented here in English translation, at the beginning of the fifth century as a revisionist history of the church and the empire in the fourth and early-fifth centuries. Sometimes contradicting and often supplementing what is found in other histories of the period, Christian or otherwise, it offers a rare dissenting picture of the Christian world of the time.

This work examines Byzantine-Bulgarian relations through the eyes of Patriarch Photios of Constantinople, one of Byzantium's greates churchmen.