Gothic War: Battle of Adrianople: A large Roman army led by Emperor Valens is defeated by the Visigoths. Valens is killed along with over half of his army.

The Gothic War of 376–382 was one of several Gothic Wars in Roman history in which the Goths fought against the Roman Empire. This particular conflict included the catastrophic Roman defeat at the Battle of Adrianople, which is commonly seen as a cause of the decline of the Western Roman Empire, although its significance is widely debated.

The Battle of Adrianople also known as Battle of Hadrianopolis was fought between the Eastern Roman army led by the Roman emperor Valens and Gothic rebels led by Fritigern. The battle took place on 9 August 378 in the vicinity of Adrianople, in the Roman province of Thracia. It ended with an overwhelming victory for the Goths and the death of Emperor Valens.

The Roman Empire ruled the Mediterranean and much of Europe, Western Asia and North Africa. The Romans conquered most of this during the Republic, and it was ruled by emperors following Octavian's assumption of effective sole rule in 27 BC. The western empire collapsed in 476 AD, but the eastern empire lasted until the fall of Constantinople in 1453.

Valens was Roman emperor from 364 to 378. Following a largely unremarkable military career, he was named co-emperor by his elder brother Valentinian I, who gave him the eastern half of the Roman Empire to rule. In 378, Valens was defeated and killed at the Battle of Adrianople against the invading Goths, which astonished contemporaries and marked the beginning of barbarian encroachment into Roman territory.

The Visigoths were a Germanic people united under the rule of a king and living within the Roman Empire during late antiquity. The Visigoths first appeared in the Balkans, as a Roman-allied barbarian military group united under the command of Alaric I. Their exact origins are believed to have been diverse but they probably included many descendants of the Thervingi who had moved into the Roman Empire beginning in 376 and had played a major role in defeating the Romans at the Battle of Adrianople in 378. Relations between the Romans and Alaric's Visigoths varied, with the two groups making treaties when convenient, and warring with one another when not. Under Alaric, the Visigoths invaded Italy and sacked Rome in August 410.