380

Year 380 (CCCLXXX) was a leap year starting on Wednesday of the Julian calendar. At the time, it was known as the Year of the Consulship of Augustus and Augustus (or, less frequently, year 1133 Ab urbe condita). The denomination 380 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

Events

February 27 – Edict of Thessalonica: Theodosius I, with co-emperors Gratian and Valentinian II, declare their wish that all Roman citizens convert to trinitarian Christianity, in accordance with the patriarchs of Rome and Alexandria, implicitly rejecting the Arianism of the patriarch of Constantinople as heretical.
Battle of Thessalonica: The Goths under Fritigern defeat a Roman army in Macedonia. Theodosius I retreats to Thessalonica and leaves Gratian in control of the Western Roman Empire.
Rome's enemies (the Germans, Sarmatians and Huns) are taken into Imperial service; as a consequence, barbarian leaders begin to play an increasingly active role in the Roman Empire.
November 24 – Theodosius I makes his adventus, or formal entry, into Constantinople.
Queen Mavia, with her Saracen forces, defeats the Roman army in southern Syria.
Emperor Theodosius I is baptized.{{cite book |last1=Omissi |first1=Adrastos |title=Emperors and Usurpers in the Later Roman Empire: Civil War, Panegyric, and the Construction of Legitimacy |date=2018 |publisher=Oxford University Press |isbn=978-0-19-882482-4 |page=282 |url=https://books.google.com/books?id=FP9eDwAAQBAJ&pg=PA282 |language=en}}

The Visigothic chieftain Fritigern dies after ravaging the Balkans; his rival Athanaric becomes king of the entire Gothic nation.

The annexation of western provinces by Chandragupta II gives him commerce with Europe and Egypt.

Easter Island, in the south Pacific Ocean, has been occupied by Neolithic seafarers under Hotu Matu'a ("supreme chief"), who about this time begin to fortify the island.

Ticonius writes a commentary on the Bible's Book of Revelation.
A cathedral is built in Augusta Treverorum.
The Council of Saragossa is held; Spanish and Aquitanian bishops condemn the teachings of Priscillianism.

Fritigern, king of the Visigoths
Samudragupta, ruler of the Gupta Empire
Wang Fahui, empress of the Jin dynasty (b. 360){{cite book |title=Urbanization in Early and Medieval China: Gazetteers for the City of Suzhou |date=1 August 2015 |publisher=University of Washington Press |isbn=978-0-295-80610-5 |page=313 |url=https://books.google.com/books?id=HhE1CgAAQBAJ&pg=PA313 |language=en}}