Ulfilas (Gothic: Wulfila) was a tireless missionary and educator among various Gothic tribes of the Western Roman Empire in the latter half of the fourth century c.e. Not only did he contribute to the culture and education of the "barbarian" tribes before they were integrated into civilized Europe, but he profoundly affected the course of Christianity in the Western Latin Church.

He was born in Cappadocia, in modern-day Turkey, probably to a Christian family. Like another great Christian missionary, Patrick, a marauding tribe captured him and taught him barbarian customs and language in his youth.

At some later point in his life he received a classical education, so that by the time he was an adult he was fluent in Greek, Latin, and the language of his former captors, Gothic. He became a priest and then was consecrated a bishop by Eusebius of Nicomedia, a leading proponent of Arianism.

His skills in languages made him a valuable asset for spreading the Christian faith. He was assigned missionary work among the Gothic tribes who were just outside the Roman Empire in the area around the lower Danube River. He did missionary work for seven years before being forced out by a hostile Visigoth chief.

Nonetheless, he persisted in his work for 30 years on both sides of the imperial border, sending out missionaries among the Visigoths and putting the Gothic language into writing. At last he succeeded at both of his projects: The Visigoths as a people became Christian, and he translated the Bible into Gothic.

The Christianity that he taught his followers was not that of the Council of Nicaea. Ulfilas apparently believed that Jesus (Christ) of Nazareth was "like" the Father and not of the same essence or being with the Father. Few of his theological writings remain, but a statement of his faith quoted by one of his students, recorded by a bishop in opposition to Ambrose of Milan, shows Arian language.

This same tendency can be found in the tribes among whom he worked. His most famous writing, however, is the Gothic Bible, done alone or with collaborators. He may have devised the first alphabet for the Goths, using a combination of Greek and Latin letters.

This achievement by itself had enormous repercussions for the transmission of Roman and Greek ideas into Gothic culture. The New Testament part of the Gothic Bible now includes only the four Gospels and the letters of Paul, and the Old Testament survives only in small parts.

The ideas of Arianism spread from the tribes with whom he worked to other Germanic groups across the Danube River. Eventually all barbarians were converted: Vandals, Burgundians, Suevi, and Lombards. When the Huns invaded and forced all of these tribal groups into Roman territory, they brought their Arianism with them and made it as big an influence in the West as it had been in the East. Were it not for emergence of the Franks—who were Orthodox Christians—Arianism might have become the predominant belief of the Latin Church.