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Christianity becomes Rome's official religion
Edict of Thessalonica (Theodosius I), AD 380· Event· Bible story & events
Historical recordConfirmed by archaeology, outside sources or contemporary records.
In 380 Emperor Theodosius I made Nicene Christianity the Roman Empire's official religion, and later banned pagan sacrifice.
See it on the Bible & Christianity map →What it is
On February 27, 380, Theodosius I and his co-emperors issued the Edict of Thessalonica: all peoples must follow the faith taught by the bishops of Rome and Alexandria, meaning the Nicene creed; others were branded heretics. In 381 he called the Council of Constantinople. Laws of 391–392 banned pagan sacrifice and closed temples. After his troops massacred thousands in Thessalonica in 390, Bishop Ambrose of Milan made him do public penance. At his death (395) the empire split for good.
Why it matters
Christianity went from persecuted to the empire's official faith in under 80 years, and the church gained the state's power to enforce orthodoxy, for good and ill.
Sources and history
The edict's text survives in the Theodosian Code (438), book 16. Ambrose's letters and later church historians record the penance.
Questions and debates
How fast paganism actually faded is debated: enforcement was uneven, and many pagans kept their practices quietly for generations.
Connections (2)
▸Christianity becomes Rome's official religion enforced The Nicene CreedHistorical record
The connection
Theodosius's 380 edict ordered everyone to follow the faith of the bishops of Rome and Alexandria, the Nicene faith, and branded others heretics. Entering Constantinople that November, he expelled its Arian bishop and installed Gregory of Nazianzus; in 381 he convened the council that expanded the creed. Later laws barred non-Nicene churches from meeting in cities.
When and where
Thessalonica, February 27, 380; Constantinople, 381.
Historical evidence
The edict and anti-heresy laws survive in the Theodosian Code (438), book 16; Gregory of Nazianzus left his own account in poems and speeches.
Questions and debates
How strictly the laws were enforced, and whether Theodosius, baptized in 380 during an illness, acted mainly from faith or for political unity, are debated.
▸Edict of Milan: tolerance for Christians was taken further by Christianity becomes Rome's official religionHistorical record
The connection
Milan (313) made Christianity legal alongside other religions. Constantine's sons restricted pagan sacrifice; Julian (361–363) tried to revive paganism; Gratian dropped the old priestly title 'pontifex maximus'. Theodosius's 380 edict then made Nicene Christianity official, and his laws of 391–392 banned pagan sacrifice: from tolerated minority to state religion in about 70 years.
When and where
Milan (313), Thessalonica (380), Constantinople (391–392).
Historical evidence
The Theodosian Code (438), book 16, collects the religious laws in order, showing the step-by-step shift.
Questions and debates
How many Romans were Christian along the way is uncertain; estimates suggest about 10% around 300 and perhaps half by 400.