Athanaric (died 381) was ruler of several branches of the Visigoths for at least two decades in the fourth century and undisputed King of the Visigoths for the last year of his life. Ironically, his Gothic name, Athanareiks, means "king for the year".

A rival of Fritigern, another Visigothic war-chief, Athanaric makes his first appearance in recorded history in 369, when he engaged in battle with the Eastern Roman Emperor Valens and ultimately negotiated a favorable peace for his people.

During his reign, the Visigoths were divided by religious issues. Many of them had converted to Arian Christianity during the third and fourth centuries, but Athanaric continued to follow the old Germanic pagan religion. Fritigern, his rival, was an Arian and had the favor of Valens, who shared his religious beliefs.

In 376, Valens permitted Fritigern's people to cross the Danube River and settle on Roman soil to avoid the Huns, who had recently conquered the Ostrogoths and were now pressing the Visigoths then living in Dacia. Athanaric's people were left to their fate, but many of them found their own way across the river, as well.

By 379, one year after Fritigern's great victory over the Romans at the Battle of Adrianople in 378, he had won over most of the Visigoths to his leadership. But he died a year later, and Athanaric became king of the entire Visigothic nation.

Shortly before his death in 381, he became the first foreign king to visit the new Roman capital of Constantinople. He negotiated a peace with the new emperor, Theodosius I that made the Visigoths foederati, or official allies of Rome allowed to settle on Roman soil as a state within a state.

A few weeks later, Athanaric died, but the treaty he made stood until Theodosius' death in 395.