|Centuries:||3rd century – 4th century – 5th century|
|Decades:||350s 360s 370s – 380s – 390s 400s 410s|
|Years:||377 378 379 – 380 – 381 382 383|
|380 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||1133|
|Chinese calendar||己卯年 (Earth Rabbit)
3076 or 3016
— to —
庚辰年 (Metal Dragon)
3077 or 3017
|- Vikram Samvat||436–437|
|- Shaka Samvat||302–303|
|- Kali Yuga||3481–3482|
|Iranian calendar||242 BP – 241 BP|
|Islamic calendar||249 BH – 248 BH|
|Minguo calendar||1532 before ROC
|Seleucid era||691/692 AG|
|Thai solar calendar||922–923|
Year 380 (CCCLXXX) was a leap year starting on Wednesday (link will display the full calendar) 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.
- January or February – Emperor Theodosius I is baptized.
- 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 control over 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 defeat with her Saracen forces the Roman army in southern Syria.
- The Rock of Cashel is built in Ireland.
- 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 give him control over 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 the fortify the island.
Arts and sciences
- Important works on mathematics and astronomy are written in Sanskrit.
- Ticonius writes a commentary on the Bible's Book of Revelation.
- A cathedral is built in Trier (Germany).
- The Council of Saragossa is held; Spanish and Aquitanian bishops condemn the teachings of Priscillianism.
- Ambrose introduces popular music into church services.
- Aelia Eudoxia, empress and wife of Arcadius (approximate date)
- Alexius, Eastern saint (approximate date)
- Eucherius, bishop of Lyon (approximate date)
- Eutyches, presbyter and archimandrite (approximate date)
- Hephaestion of Thebes, Egyptian astrologer (approximate date)
- Kālidāsa, Classical Sanskrit writer (approximate date)
- Olympiodorus of Thebes, historical writer (approximate date)
- Peter Chrysologus, bishop of Ravenna (approximate date)
- Philip of Side, Christian church historian (approximate date)
- Socrates of Constantinople, church historian (approximate date)
- Fritigern, king of the Visigoths
- Pope Peter II of Alexandria
- Samudragupta, ruler of the Gupta Empire
- Wang Fahui, empress of the Jin dynasty (b. 360)