Year 391 (Common year in the Julian calendar)

Summary of year 391 CE: calendar context, major events in the late Roman Empire—especially Theodosius I's anti-pagan measures and the Serapeum's destruction—and its historical significance.

Year 391 was a common year in the Julian calendar, a 365-day year not preceded by a leap day. The year is most frequently discussed by historians in the context of the late Roman Empire and the accelerating transition from Roman religious pluralism toward a Christian imperial establishment. For calendar background, see Julian calendar.

Overview

The principal developments recorded for 391 center on imperial legislation and religious conflict. Under Emperor Theodosius I, imperial policy increasingly favored Nicene Christianity and sought to curtail traditional pagan practices. These measures were part of a broader trend in the fourth century that transformed public cults, temple administration, and the role of bishops in imperial affairs.

Notable events

Imperial laws and enforcement: Theodosius and his court promulgated laws restricting pagan sacrifices and public rites. These laws strengthened the legal position of Christian institutions and reduced official toleration for traditional polytheistic worship.
Destruction of the Serapeum in Alexandria: In the same period, a long-standing pagan center—the Serapeum—was sacked and its buildings damaged or destroyed in confrontations involving Christian crowds and local authorities. The episode is often cited as a symbol of the decline of organized pagan cult activity in major cities.

Contemporary ecclesiastical leaders, notably influential bishops, played a prominent role in shaping how imperial directives were implemented at the local level. The available sources for 391 are largely ecclesiastical or imperial legal compilations, and they reflect the religious and political priorities of their authors.

Significance and consequences

The events of 391 did not end paganism overnight, but they marked a decisive turn in state policy: temple revenues, public rites, and official recognition of polytheistic cults were curtailed in many regions. Over subsequent decades this contributed to the reconfiguration of religious life in the Roman world, the rise of Christian institutions as civic authorities, and the repurposing or abandonment of temple buildings.

Outside the Roman sphere, regional polities continued their own developments; records from other areas are fragmentary and preserved in distinct traditions. Historians regard 391 as a representative year in the late fourth century that illustrates wider cultural and administrative shifts rather than as a moment defined by a single, universally transformative event.