By place

Roman Empire

• Spring – Emperor Valens returns to Constantinople and mobilises an army (40,000 men). He appoints Sebastian, newly arrived from Italy, as magister militum to reorganize the Roman armies in Thrace.
• February – The Lentienses (part of the Alemanni) cross the frozen Rhine and raid the countryside. They are driven back by Roman auxilia palatina (Celtae and Petulantes), who defend the western frontier.
• May – Battle of Argentovaria: Emperor Gratian is forced to recall the army he has sent East. The Lentienses are defeated by Mallobaudes near Colmar (France). Gratian gains the title Alemannicus Maximus.
• Gothic War: Valens sends Sebastian with a body of picked troops (2,000 men) to Thrace and renews the guerrilla war against the Goths. He chases down small groups of Gothic raiders around Adrianople.
• Fritigern concentrates his army at Cabyle (Bulgaria). The Goths are mainly centred in the river valleys south of the Balkan Mountains, around the towns of Beroea, Cabyle and Dibaltum.
• July – Frigeridus, Roman general, fortifies the Succi (Ihtiman) Pass to prevent the "barbarians" from breaking out to the north-west (Pannonia).
• Gratian sets out from Lauriacum (Austria) with a body of light armed troops. His force is small enough to travel by boat down the Danube. He halts for four days at Sirmium (Serbia) suffering from fever.
• August – Gratian continues down the Danube to the "Camp of Mars" (frontier fortress near modern Niš), where he loses several men in an ambush by a band of Alans.
• Fritigern strikes south from Cabyle, following the Tundzha River towards Adrianople, and tries to get behind the supply lines to Constantinople.
• Roman reconnaissance detects the Goths. Valens, already west of Adrianople, returns back and establishes a fortified camp outside the city.
• The Goths, with their wagons and families vulnerable to attack, withdraw back to the north. Roman scouts fail to detect the Greuthungi cavalry foraging further up the Tundzha valley.
• Fritigern sends a Christian priest to the Roman camp with an offer of terms and a letter for Valens. The peace overtures are rejected.
• August 9 – Battle of Adrianople: A large Roman army is defeated by the Thervingi. Valens is killed along with two-thirds of his army.
• The Goths attack Adrianople; they attempt to scale the city walls with ladders but are repelled by the defenders, who drop lumps of masonry.
• The Goths, supported by the Huns, move on to Constantinople. Their progress is checked by the Saracens, recruited from Arab tribes who control the eastern fringes of the empire.
• October – The Greuthungi, faced with food shortages, split off and move west into Pannonia. Followed by their families, they raid villages and farmland.
• Gratian recalls his military commander Flavius Theodosius, age 31, son of the executed general Theodosius the Elder, and appoints him co-emperor of the Eastern Roman Empire.

Mesoamerica

• Siyaj K'ak' begins to replace Mayan kings with relatives of Spearthrower Owl, emperor of Teotihuacan.
• Siyaj K'ak' conquers Waka on January 8.
• Siyaj K'ak' conquers Tikal on January 16.
• Siyaj K'ak' conquers Uaxactun.

By topic

Architecture

• Valens completes the aqueduct of Constantinople begun by Constantine I.

Religion

• Gregory of Nazianzus is ordained bishop of Constantinople.
• Pope Damasus I is accused of adultery but is exonerated by Gratian.