Theodosius Makes Nicene Christianity the Empire's Official Religion
The Edict of Thessalonica orders every subject to hold the faith of Peter, on penalty of the emperor's judgment
Quick facts
- Date
- February 27, 380 CE
- Issued by
- Theodosius I, Gratian, Valentinian II
- Recorded in
- Codex Theodosianus, Book 16.1.2
- Effect
- Made Nicene Christianity the sole legal state religion
What happened
Emperor Theodosius I, together with co-emperors Gratian and Valentinian II, issued an edict in 380 CE commanding that all peoples under their rule should hold to the religion handed down by the apostle Peter to the Romans, professed by Pope Damasus and by Peter, bishop of Alexandria, and affirming belief in the Father, Son, and Holy Spirit as equal in majesty within a single Trinity. The edict, recorded in the Theodosian legal code, named this Nicene position the only faith entitled to be called Catholic and threatened those who dissented with what it called the judgment of divine condemnation, later followed by concrete legal penalties against groups like the Arians. Where the Edict of Milan in 313 CE had granted toleration to all religions, this edict went further, establishing a single specific Christian creed as the empire's law.
Why it matters
This edict turned Nicene Christianity from a tolerated and imperially favored religion into the compulsory state religion of the Roman Empire, ending the era of pagan and heterodox Christian practice as a legally protected option and setting the template European states would follow for religious establishment for the next fourteen centuries.
How we know
The edict is preserved in Book 16 of the Codex Theodosianus, the official compilation of Roman imperial law completed in 438 CE, an administrative record rather than a religious composition.
Sources
- Internet History Sourcebooks Project, Fordham University. The Theodosian Code, Book XVI · Primary source (author-declared)sourcebooks.fordham.edu · Cited as a "primary" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
- Internet History Sourcebooks Project, Fordham University. Codex Theodosianus · Primary source (author-declared)sourcebooks.fordham.edu · Cited as a "primary" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
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Part of a timelineHistory of Christianity28 events · A crucified Jewish teacher, a persecuted sect that became an empire's official religion, and two thousand years of councils, schisms, and missions that carried it to every continentView all →