Philostorgius (Greek: Φιλοστόργιος; 368 – c. 439 AD) was an Anomoean Church historian of the 4th and 5th centuries. Anomoeanism questioned the Trinitarian account of the relationship between God the Father and Christ and was considered heretical by the Church, which adopted the term "homoousion", or "consubstantial", to describe the relation between Father and Son in the Nicene Creed.
Very little information about his life is available. He was born in Borissus, Cappadocia to Eulampia and Carterius, and lived in Constantinople from the age of twenty. He is said to have come from an Arian family, and in Constantinople soon attached himself to Eunomius, who receives a lot of praise from Philostorgius in his work.
He wrote a history of the Arian controversy titled Church History (Ἐκκλησιαστικὴ ἱστορία). Philostorgius' original appeared between 425 and 433, in other words, slightly earlier than the History of Socrates of Constantinople, and was formed in twelve volumes bound in two books. The original is now lost. However, one copy was found by the ninth-century historian Photius, in his library in Constantinople, who wrote an epitome of it. Others also borrowed from Philostorgius, most notably the author of the Artemii Passio (Artemius being a legendary martyr under Julian the Apostate), and so, despite the eventual disappearance of the original text, it is possible to form some idea of what it contained by reviewing the epitome and other references. This reconstruction of what might have been in the text was first published, in German, by the Belgian philologist Joseph Bidez in 1913; a third, revised edition of his work undertaken by Friedhelm Winkelmann was published in 1981; this edition has recently been translated into English by Philip R. Amidon.